diff --git a/cmake/externals/oglplus/CMakeLists.txt b/cmake/externals/oglplus/CMakeLists.txt
index 43730129a0..089ee5bb95 100644
--- a/cmake/externals/oglplus/CMakeLists.txt
+++ b/cmake/externals/oglplus/CMakeLists.txt
@@ -4,7 +4,7 @@ string(TOUPPER ${EXTERNAL_NAME} EXTERNAL_NAME_UPPER)
 include(ExternalProject)
 ExternalProject_Add(
     ${EXTERNAL_NAME}
-    URL http://iweb.dl.sourceforge.net/project/oglplus/oglplus-0.63.x/oglplus-0.63.0.zip
+    URL http://hifi-public.s3.amazonaws.com/dependencies/oglplus-0.63.0.zip
     URL_MD5 de984ab245b185b45c87415c0e052135
     CONFIGURE_COMMAND ""
     BUILD_COMMAND ""
diff --git a/interface/resources/qml/ToolWindow.qml b/interface/resources/qml/ToolWindow.qml
index 404d1c1e78..75aa50aa34 100644
--- a/interface/resources/qml/ToolWindow.qml
+++ b/interface/resources/qml/ToolWindow.qml
@@ -17,7 +17,6 @@ Windows.Window {
     visible: false
     width: 384; height: 640;
     title: "Tools"
-    property string newTabSource
     property alias tabView: tabView
     onParentChanged: {
         if (parent) {
@@ -32,26 +31,21 @@ Windows.Window {
         property alias y: toolWindow.y
     }
 
-    property var webTabCreator: Component {
-        Controls.WebView {
-            id: webView
-            property string originalUrl;
-
-            // Both toolWindow.newTabSource and url can change, so we need
-            // to store the original url here, without creating any bindings
-            Component.onCompleted: {
-                originalUrl = toolWindow.newTabSource;
-                url = originalUrl;
-            }
-        }
-    }
-
     TabView {
         anchors.fill: parent
         id: tabView;
-        onCountChanged: {
-            if (0 == count) {
-                toolWindow.visible = false
+        Repeater {
+            model: 4
+            Tab {
+                active: true
+                enabled: false;
+                // we need to store the original url here for future identification
+                property string originalUrl: "";
+                onEnabledChanged: toolWindow.updateVisiblity();
+                Controls.WebView {
+                    id: webView;
+                    anchors.fill: parent
+                }
             }
         }
     }
@@ -68,8 +62,7 @@ Windows.Window {
     function findIndexForUrl(source) {
         for (var i = 0; i < tabView.count; ++i) {
             var tab = tabView.getTab(i);
-            if (tab && tab.item && tab.item.originalUrl &&
-                tab.item.originalUrl === source) {
+            if (tab.originalUrl === source) {
                 return i;
             }
         }
@@ -101,21 +94,32 @@ Windows.Window {
         }
     }
 
+    function findFreeTab() {
+        for (var i = 0; i < tabView.count; ++i) {
+            var tab = tabView.getTab(i);
+            if (tab && (!tab.originalUrl || tab.originalUrl === "")) {
+                return i;
+            }
+        }
+        console.warn("Could not find free tab");
+        return -1;
+    }
+
     function removeTabForUrl(source) {
         var index = findIndexForUrl(source);
         if (index < 0) {
             return;
         }
+
         var tab = tabView.getTab(index);
-        tab.enabledChanged.disconnect(updateVisiblity);
-        tabView.removeTab(index);
-        console.log("Updating visibility based on child tab removed");
-        updateVisiblity();
+        tab.title = "";
+        tab.originalUrl = "";
+        tab.enabled = false;
     }
 
     function addWebTab(properties) {
         if (!properties.source) {
-            console.warn("Attempted to open Web Tool Pane without URl")
+            console.warn("Attempted to open Web Tool Pane without URL")
             return;
         }
 
@@ -125,11 +129,17 @@ Windows.Window {
             return tabView.getTab(existingTabIndex);
         }
 
-        var title = properties.title || "Unknown";
-        newTabSource = properties.source;
-        var newTab = tabView.addTab(title, webTabCreator);
+        var freeTabIndex = findFreeTab();
+        if (freeTabIndex === -1) {
+            console.warn("Unable to add new tab");
+            return;
+        }
+
+        var newTab = tabView.getTab(freeTabIndex);
+        newTab.title = properties.title || "Unknown";
+        newTab.originalUrl = properties.source;
+        newTab.item.url = properties.source;
         newTab.active = true;
-        newTab.enabled = false;
 
         if (properties.width) {
             tabView.width = Math.min(Math.max(tabView.width, properties.width),
diff --git a/interface/src/Application.cpp b/interface/src/Application.cpp
index 06755ae70a..ad25160dd7 100644
--- a/interface/src/Application.cpp
+++ b/interface/src/Application.cpp
@@ -239,11 +239,7 @@ class DeadlockWatchdogThread : public QThread {
 public:
     static const unsigned long HEARTBEAT_CHECK_INTERVAL_SECS = 1;
     static const unsigned long HEARTBEAT_UPDATE_INTERVAL_SECS = 1;
-#ifdef DEBUG
-    static const unsigned long MAX_HEARTBEAT_AGE_USECS = 600 * USECS_PER_SECOND;
-#else
     static const unsigned long MAX_HEARTBEAT_AGE_USECS = 10 * USECS_PER_SECOND;
-#endif
 
     // Set the heartbeat on launch
     DeadlockWatchdogThread() {
@@ -511,8 +507,8 @@ Application::Application(int& argc, char** argv, QElapsedTimer& startupTimer) :
     auto nodeList = DependencyManager::get<NodeList>();
 
     // Set up a watchdog thread to intentionally crash the application on deadlocks
-    auto deadlockWatchdog = new DeadlockWatchdogThread();
-    deadlockWatchdog->start();
+    _deadlockWatchdogThread = new DeadlockWatchdogThread();
+    _deadlockWatchdogThread->start();
 
     qCDebug(interfaceapp) << "[VERSION] Build sequence:" << qPrintable(applicationVersion());
 
@@ -586,7 +582,7 @@ Application::Application(int& argc, char** argv, QElapsedTimer& startupTimer) :
 
     ResourceManager::init();
     // Make sure we don't time out during slow operations at startup
-    deadlockWatchdog->updateHeartbeat();
+    updateHeartbeat();
 
     // Setup MessagesClient
     auto messagesClient = DependencyManager::get<MessagesClient>();
@@ -734,7 +730,7 @@ Application::Application(int& argc, char** argv, QElapsedTimer& startupTimer) :
     initializeGL();
     _offscreenContext->makeCurrent();
     // Make sure we don't time out during slow operations at startup
-    deadlockWatchdog->updateHeartbeat();
+    updateHeartbeat();
 
     // Tell our entity edit sender about our known jurisdictions
     _entityEditSender.setServerJurisdictions(&_entityServerJurisdictions);
@@ -746,7 +742,7 @@ Application::Application(int& argc, char** argv, QElapsedTimer& startupTimer) :
 
     _overlays.init(); // do this before scripts load
     // Make sure we don't time out during slow operations at startup
-    deadlockWatchdog->updateHeartbeat();
+    updateHeartbeat();
 
     connect(this, SIGNAL(aboutToQuit()), this, SLOT(aboutToQuit()));
 
@@ -900,11 +896,11 @@ Application::Application(int& argc, char** argv, QElapsedTimer& startupTimer) :
     // do this as late as possible so that all required subsystems are initialized
     scriptEngines->loadScripts();
     // Make sure we don't time out during slow operations at startup
-    deadlockWatchdog->updateHeartbeat();
+    updateHeartbeat();
 
     loadSettings();
     // Make sure we don't time out during slow operations at startup
-    deadlockWatchdog->updateHeartbeat();
+    updateHeartbeat();
 
     int SAVE_SETTINGS_INTERVAL = 10 * MSECS_PER_SECOND; // Let's save every seconds for now
     connect(&_settingsTimer, &QTimer::timeout, this, &Application::saveSettings);
@@ -1019,7 +1015,7 @@ Application::Application(int& argc, char** argv, QElapsedTimer& startupTimer) :
     });
 
     // Make sure we don't time out during slow operations at startup
-    deadlockWatchdog->updateHeartbeat();
+    updateHeartbeat();
 
     connect(this, &Application::applicationStateChanged, this, &Application::activeChanged);
     qCDebug(interfaceapp, "Startup time: %4.2f seconds.", (double)startupTimer.elapsed() / 1000.0);
@@ -1060,6 +1056,10 @@ void Application::showCursor(const QCursor& cursor) {
     _cursorNeedsChanging = true;
 }
 
+void Application::updateHeartbeat() {
+    static_cast<DeadlockWatchdogThread*>(_deadlockWatchdogThread)->updateHeartbeat();
+}
+
 void Application::aboutToQuit() {
     emit beforeAboutToQuit();
 
diff --git a/interface/src/Application.h b/interface/src/Application.h
index 4c12164a5f..3b906a7d17 100644
--- a/interface/src/Application.h
+++ b/interface/src/Application.h
@@ -271,6 +271,8 @@ public slots:
 
     void reloadResourceCaches();
 
+    void updateHeartbeat();
+
     void crashApplication();
     void deadlockApplication();
 
@@ -505,6 +507,8 @@ private:
     mutable QMutex _changeCursorLock { QMutex::Recursive };
     QCursor _desiredCursor{ Qt::BlankCursor };
     bool _cursorNeedsChanging { false };
+
+    QThread* _deadlockWatchdogThread;
 };
 
 #endif // hifi_Application_h
diff --git a/libraries/avatars/src/AvatarData.cpp b/libraries/avatars/src/AvatarData.cpp
index 93d2ebb5da..290aaff820 100644
--- a/libraries/avatars/src/AvatarData.cpp
+++ b/libraries/avatars/src/AvatarData.cpp
@@ -968,9 +968,10 @@ bool AvatarData::hasIdentityChangedAfterParsing(const QByteArray& data) {
 
     bool hasIdentityChanged = false;
 
-    if (skeletonModelURL != _skeletonModelURL) {
+    if (_firstSkeletonCheck || (skeletonModelURL != _skeletonModelURL)) {
         setSkeletonModelURL(skeletonModelURL);
         hasIdentityChanged = true;
+        _firstSkeletonCheck = false;
     }
 
     if (displayName != _displayName) {
diff --git a/libraries/avatars/src/AvatarData.h b/libraries/avatars/src/AvatarData.h
index 8a6b558383..900da38ffa 100644
--- a/libraries/avatars/src/AvatarData.h
+++ b/libraries/avatars/src/AvatarData.h
@@ -368,7 +368,8 @@ protected:
 
     HeadData* _headData;
 
-    QUrl _skeletonModelURL; // These need to be empty so that on first time setting them they will not short circuit
+    QUrl _skeletonModelURL;
+    bool _firstSkeletonCheck { true };
     QUrl _skeletonFBXURL;
     QVector<AttachmentData> _attachmentData;
     QString _displayName;
diff --git a/libraries/fbx/src/FBXReader.cpp b/libraries/fbx/src/FBXReader.cpp
index b2ede33e01..de8c001566 100644
--- a/libraries/fbx/src/FBXReader.cpp
+++ b/libraries/fbx/src/FBXReader.cpp
@@ -78,10 +78,14 @@ bool FBXGeometry::convexHullContains(const glm::vec3& point) const {
 
     auto checkEachPrimitive = [=](FBXMesh& mesh, QVector<int> indices, int primitiveSize) -> bool {
         // Check whether the point is "behind" all the primitives.
+        int verticesSize = mesh.vertices.size();
         for (int j = 0;
              j < indices.size() - 2; // -2 in case the vertices aren't the right size -- we access j + 2 below
              j += primitiveSize) {
-            if (!isPointBehindTrianglesPlane(point,
+            if (indices[j] < verticesSize &&
+                indices[j + 1] < verticesSize &&
+                indices[j + 2] < verticesSize &&
+                !isPointBehindTrianglesPlane(point,
                                              mesh.vertices[indices[j]],
                                              mesh.vertices[indices[j + 1]],
                                              mesh.vertices[indices[j + 2]])) {
diff --git a/libraries/gl/src/gl/OffscreenGLCanvas.cpp b/libraries/gl/src/gl/OffscreenGLCanvas.cpp
index 7406577814..31bbc84cb2 100644
--- a/libraries/gl/src/gl/OffscreenGLCanvas.cpp
+++ b/libraries/gl/src/gl/OffscreenGLCanvas.cpp
@@ -44,12 +44,6 @@ bool OffscreenGLCanvas::create(QOpenGLContext* sharedContext) {
         return true;
     }
 
-    qWarning() << "GL Version: " << QString((const char*) glGetString(GL_VERSION));
-    qWarning() << "GL Shader Language Version: " << QString((const char*) glGetString(GL_SHADING_LANGUAGE_VERSION));
-    qWarning() << "GL Vendor: " << QString((const char*) glGetString(GL_VENDOR));
-    qWarning() << "GL Renderer: " << QString((const char*) glGetString(GL_RENDERER));
-    qWarning() << "Failed to create OffscreenGLCanvas";
-
     return false;
 }
 
diff --git a/libraries/gl/src/gl/OffscreenQmlSurface.cpp b/libraries/gl/src/gl/OffscreenQmlSurface.cpp
index 0a3598e840..4cfd2527ea 100644
--- a/libraries/gl/src/gl/OffscreenQmlSurface.cpp
+++ b/libraries/gl/src/gl/OffscreenQmlSurface.cpp
@@ -187,6 +187,15 @@ bool OffscreenQmlRenderThread::event(QEvent *e) {
 void OffscreenQmlRenderThread::setupFbo() {
     using namespace oglplus;
     _textures.setSize(_size);
+
+    // Before making any ogl calls, clear any outstanding errors
+    // FIXME: Something upstream is polluting the context with a GL_INVALID_ENUM,
+    //        likely from glewExperimental = true
+    GLenum err = glGetError();
+    if (err != GL_NO_ERROR) {
+        qDebug() << "Clearing outstanding GL error to set up QML FBO:" << glewGetErrorString(err);
+    }
+
     _depthStencil.reset(new Renderbuffer());
     Context::Bound(Renderbuffer::Target::Renderbuffer, *_depthStencil)
         .Storage(
@@ -417,7 +426,11 @@ void OffscreenQmlSurface::setBaseUrl(const QUrl& baseUrl) {
 }
 
 QObject* OffscreenQmlSurface::load(const QUrl& qmlSource, std::function<void(QQmlContext*, QObject*)> f) {
-    _qmlComponent->loadUrl(qmlSource);
+    // Synchronous loading may take a while; restart the deadlock timer
+    QMetaObject::invokeMethod(qApp, "updateHeartbeat", Qt::DirectConnection);
+
+    _qmlComponent->loadUrl(qmlSource, QQmlComponent::PreferSynchronous);
+
     if (_qmlComponent->isLoading()) {
         connect(_qmlComponent, &QQmlComponent::statusChanged, this, 
             [this, f](QQmlComponent::Status){
diff --git a/libraries/gpu/src/gpu/GLBackend.cpp b/libraries/gpu/src/gpu/GLBackend.cpp
index 14e4397b83..2c25255a80 100644
--- a/libraries/gpu/src/gpu/GLBackend.cpp
+++ b/libraries/gpu/src/gpu/GLBackend.cpp
@@ -87,18 +87,15 @@ void GLBackend::init() {
     static std::once_flag once;
     std::call_once(once, [] {
         qCDebug(gpulogging) << "GL Version: " << QString((const char*) glGetString(GL_VERSION));
-
         qCDebug(gpulogging) << "GL Shader Language Version: " << QString((const char*) glGetString(GL_SHADING_LANGUAGE_VERSION));
-
         qCDebug(gpulogging) << "GL Vendor: " << QString((const char*) glGetString(GL_VENDOR));
-
         qCDebug(gpulogging) << "GL Renderer: " << QString((const char*) glGetString(GL_RENDERER));
 
         glewExperimental = true;
         GLenum err = glewInit();
-        glGetError();
+        glGetError(); // clear the potential error from glewExperimental
         if (GLEW_OK != err) {
-            /* Problem: glewInit failed, something is seriously wrong. */
+            // glewInit failed, something is seriously wrong.
             qCDebug(gpulogging, "Error: %s\n", glewGetErrorString(err));
         }
         qCDebug(gpulogging, "Status: Using GLEW %s\n", glewGetString(GLEW_VERSION));
diff --git a/libraries/gpu/src/gpu/Resource.cpp b/libraries/gpu/src/gpu/Resource.cpp
index 1788f6ece5..197263f392 100644
--- a/libraries/gpu/src/gpu/Resource.cpp
+++ b/libraries/gpu/src/gpu/Resource.cpp
@@ -10,11 +10,74 @@
 //
 #include "Resource.h"
 
+#include <atomic>
+
+#include <SharedUtil.h>
+#include <NumericalConstants.h>
 #include <QDebug>
 
 using namespace gpu;
 
+class AllocationDebugger {
+public:
+    void operator+=(size_t size) {
+        _allocatedMemory += size;
+        maybeReport();
+    }
+
+    void operator-=(size_t size) {
+        _allocatedMemory -= size;
+        maybeReport();
+    }
+
+private:
+    QString formatSize(size_t size) {
+        float num = size;
+        QStringList list;
+        list << "KB" << "MB" << "GB" << "TB";
+
+        QStringListIterator i(list);
+        QString unit("bytes");
+
+        while (num >= K && i.hasNext()) {
+            unit = i.next();
+            num /= K;
+        }
+        return QString().setNum(num, 'f', 2) + " " + unit;
+    }
+
+    void maybeReport() {
+        auto now = usecTimestampNow();
+        if (now - _lastReportTime < MAX_REPORT_FREQUENCY) {
+            return;
+        }
+        size_t current = _allocatedMemory;
+        size_t last = _lastReportedMemory;
+        size_t delta = (current > last) ? (current - last) : (last - current);
+        if (delta > MIN_REPORT_DELTA) {
+            _lastReportTime = now;
+            _lastReportedMemory = current;
+            qDebug() << "Total allocation " << formatSize(current);
+        }
+    }
+
+    std::atomic<size_t> _allocatedMemory;
+    std::atomic<size_t> _lastReportedMemory;
+    std::atomic<uint64_t> _lastReportTime;
+
+    static const float K;
+    // Report changes of 5 megabytes
+    static const size_t MIN_REPORT_DELTA = 1024 * 1024 * 5;
+    // Report changes no more frequently than every 15 seconds
+    static const uint64_t MAX_REPORT_FREQUENCY = USECS_PER_SECOND * 15;
+};
+
+const float AllocationDebugger::K = 1024.0f;
+
+static AllocationDebugger allocationDebugger;
+
 Resource::Size Resource::Sysmem::allocateMemory(Byte** dataAllocated, Size size) {
+    allocationDebugger += size;
     if ( !dataAllocated ) { 
         qWarning() << "Buffer::Sysmem::allocateMemory() : Must have a valid dataAllocated pointer.";
         return NOT_ALLOCATED;
@@ -38,6 +101,7 @@ Resource::Size Resource::Sysmem::allocateMemory(Byte** dataAllocated, Size size)
 }
 
 void Resource::Sysmem::deallocateMemory(Byte* dataAllocated, Size size) {
+    allocationDebugger -= size;
     if (dataAllocated) {
         delete[] dataAllocated;
     }
diff --git a/libraries/render-utils/src/Model.cpp b/libraries/render-utils/src/Model.cpp
index 16db6532da..0a483914df 100644
--- a/libraries/render-utils/src/Model.cpp
+++ b/libraries/render-utils/src/Model.cpp
@@ -29,7 +29,7 @@
 
 using namespace std;
 
-static int modelPointerTypeId = qRegisterMetaType<QPointer<Model> >();
+static int nakedModelPointerTypeId = qRegisterMetaType<ModelPointer>();
 static int weakNetworkGeometryPointerTypeId = qRegisterMetaType<QWeakPointer<NetworkGeometry> >();
 static int vec3VectorTypeId = qRegisterMetaType<QVector<glm::vec3> >();
 float Model::FAKE_DIMENSION_PLACEHOLDER = -1.0f;
@@ -821,21 +821,21 @@ QStringList Model::getJointNames() const {
 class Blender : public QRunnable {
 public:
 
-    Blender(Model* model, int blendNumber, const QWeakPointer<NetworkGeometry>& geometry,
+    Blender(ModelPointer model, int blendNumber, const QWeakPointer<NetworkGeometry>& geometry,
         const QVector<FBXMesh>& meshes, const QVector<float>& blendshapeCoefficients);
 
     virtual void run();
 
 private:
 
-    QPointer<Model> _model;
+    ModelPointer _model;
     int _blendNumber;
     QWeakPointer<NetworkGeometry> _geometry;
     QVector<FBXMesh> _meshes;
     QVector<float> _blendshapeCoefficients;
 };
 
-Blender::Blender(Model* model, int blendNumber, const QWeakPointer<NetworkGeometry>& geometry,
+Blender::Blender(ModelPointer model, int blendNumber, const QWeakPointer<NetworkGeometry>& geometry,
         const QVector<FBXMesh>& meshes, const QVector<float>& blendshapeCoefficients) :
     _model(model),
     _blendNumber(blendNumber),
@@ -847,7 +847,7 @@ Blender::Blender(Model* model, int blendNumber, const QWeakPointer<NetworkGeomet
 void Blender::run() {
     PROFILE_RANGE(__FUNCTION__);
     QVector<glm::vec3> vertices, normals;
-    if (!_model.isNull()) {
+    if (_model) {
         int offset = 0;
         foreach (const FBXMesh& mesh, _meshes) {
             if (mesh.blendshapes.isEmpty()) {
@@ -877,7 +877,7 @@ void Blender::run() {
     }
     // post the result to the geometry cache, which will dispatch to the model if still alive
     QMetaObject::invokeMethod(DependencyManager::get<ModelBlender>().data(), "setBlendedVertices",
-        Q_ARG(const QPointer<Model>&, _model), Q_ARG(int, _blendNumber),
+        Q_ARG(ModelPointer, _model), Q_ARG(int, _blendNumber),
         Q_ARG(const QWeakPointer<NetworkGeometry>&, _geometry), Q_ARG(const QVector<glm::vec3>&, vertices),
         Q_ARG(const QVector<glm::vec3>&, normals));
 }
@@ -1088,7 +1088,7 @@ float Model::getLimbLength(int jointIndex) const {
 bool Model::maybeStartBlender() {
     const FBXGeometry& fbxGeometry = _geometry->getFBXGeometry();
     if (fbxGeometry.hasBlendedMeshes()) {
-        QThreadPool::globalInstance()->start(new Blender(this, ++_blendNumber, _geometry,
+        QThreadPool::globalInstance()->start(new Blender(getThisPointer(), ++_blendNumber, _geometry,
             fbxGeometry.meshes, _blendshapeCoefficients));
         return true;
     }
@@ -1277,20 +1277,25 @@ void ModelBlender::noteRequiresBlend(ModelPointer model) {
         }
         return;
     }
-    _modelsRequiringBlends.insert(model);
+
+    {
+        Lock lock(_mutex);
+        _modelsRequiringBlends.insert(model);
+    }
 }
 
-void ModelBlender::setBlendedVertices(const QPointer<Model>& model, int blendNumber,
+void ModelBlender::setBlendedVertices(ModelPointer model, int blendNumber,
         const QWeakPointer<NetworkGeometry>& geometry, const QVector<glm::vec3>& vertices, const QVector<glm::vec3>& normals) {
-    if (!model.isNull()) {
+    if (model) {
         model->setBlendedVertices(blendNumber, geometry, vertices, normals);
     }
     _pendingBlenders--;
-    while (!_modelsRequiringBlends.empty()) {
-        auto firstItem = _modelsRequiringBlends.begin();
-        if (firstItem != _modelsRequiringBlends.end()) {
-            _modelsRequiringBlends.erase(firstItem);
-            ModelPointer nextModel = firstItem->lock();
+    {
+        Lock lock(_mutex);
+        for (auto i = _modelsRequiringBlends.begin(); i != _modelsRequiringBlends.end();) {
+            auto weakPtr = *i;
+            _modelsRequiringBlends.erase(i++); // remove front of the set
+            ModelPointer nextModel = weakPtr.lock();
             if (nextModel && nextModel->maybeStartBlender()) {
                 _pendingBlenders++;
                 return;
diff --git a/libraries/render-utils/src/Model.h b/libraries/render-utils/src/Model.h
index 1e8b3f2af6..4e51dc4f33 100644
--- a/libraries/render-utils/src/Model.h
+++ b/libraries/render-utils/src/Model.h
@@ -384,7 +384,7 @@ protected:
     RigPointer _rig;
 };
 
-Q_DECLARE_METATYPE(QPointer<Model>)
+Q_DECLARE_METATYPE(ModelPointer)
 Q_DECLARE_METATYPE(QWeakPointer<NetworkGeometry>)
 
 /// Handle management of pending models that need blending
@@ -398,15 +398,19 @@ public:
     void noteRequiresBlend(ModelPointer model);
 
 public slots:
-    void setBlendedVertices(const QPointer<Model>& model, int blendNumber, const QWeakPointer<NetworkGeometry>& geometry,
+    void setBlendedVertices(ModelPointer model, int blendNumber, const QWeakPointer<NetworkGeometry>& geometry,
         const QVector<glm::vec3>& vertices, const QVector<glm::vec3>& normals);
 
 private:
+    using Mutex = std::mutex;
+    using Lock = std::unique_lock<Mutex>;
+
     ModelBlender();
     virtual ~ModelBlender();
 
     std::set<ModelWeakPointer, std::owner_less<ModelWeakPointer>> _modelsRequiringBlends;
     int _pendingBlenders;
+    Mutex _mutex;
 };
 
 
diff --git a/libraries/ui/src/QmlWindowClass.cpp b/libraries/ui/src/QmlWindowClass.cpp
index 5bd40b10a9..e986ea0441 100644
--- a/libraries/ui/src/QmlWindowClass.cpp
+++ b/libraries/ui/src/QmlWindowClass.cpp
@@ -172,7 +172,6 @@ QScriptValue QmlWindowClass::internalConstructor(const QString& qmlSource,
             setupServer();
             retVal = builder(newTab);
             retVal->_toolWindow = true;
-            offscreenUi->getRootContext()->engine()->setObjectOwnership(retVal->_qmlWindow, QQmlEngine::CppOwnership);
             registerObject(url.toLower(), retVal);
             return QVariant();
         });
@@ -330,10 +329,8 @@ void QmlWindowClass::close() {
     if (_qmlWindow) {
         if (_toolWindow) {
             auto offscreenUi = DependencyManager::get<OffscreenUi>();
-            auto qmlWindow = _qmlWindow;
             offscreenUi->executeOnUiThread([=] {
                 auto toolWindow = offscreenUi->getToolWindow();
-                offscreenUi->getRootContext()->engine()->setObjectOwnership(qmlWindow, QQmlEngine::JavaScriptOwnership);
                 auto invokeResult = QMetaObject::invokeMethod(toolWindow, "removeTabForUrl", Qt::DirectConnection,
                     Q_ARG(QVariant, _source));
                 Q_ASSERT(invokeResult);
diff --git a/plugins/oculus/src/OculusBaseDisplayPlugin.cpp b/plugins/oculus/src/OculusBaseDisplayPlugin.cpp
index 9d0838606e..29fc014a64 100644
--- a/plugins/oculus/src/OculusBaseDisplayPlugin.cpp
+++ b/plugins/oculus/src/OculusBaseDisplayPlugin.cpp
@@ -30,7 +30,7 @@ bool OculusBaseDisplayPlugin::isSupported() const {
 void OculusBaseDisplayPlugin::customizeContext() {
     glewExperimental = true;
     GLenum err = glewInit();
-    glGetError();
+    glGetError(); // clear the potential error from glewExperimental
     Parent::customizeContext();
 }
 
diff --git a/plugins/openvr/src/OpenVrDisplayPlugin.cpp b/plugins/openvr/src/OpenVrDisplayPlugin.cpp
index 07629a442f..b479c19fb4 100644
--- a/plugins/openvr/src/OpenVrDisplayPlugin.cpp
+++ b/plugins/openvr/src/OpenVrDisplayPlugin.cpp
@@ -104,7 +104,7 @@ void OpenVrDisplayPlugin::customizeContext() {
     std::call_once(once, []{
         glewExperimental = true;
         GLenum err = glewInit();
-        glGetError();
+        glGetError(); // clear the potential error from glewExperimental
     });
     Parent::customizeContext();
 }