diff --git a/libraries/script-engine/src/v8/ScriptEngineV8_cast.cpp b/libraries/script-engine/src/v8/ScriptEngineV8_cast.cpp
index 1552d17c03..cf5512df8b 100644
--- a/libraries/script-engine/src/v8/ScriptEngineV8_cast.cpp
+++ b/libraries/script-engine/src/v8/ScriptEngineV8_cast.cpp
@@ -344,6 +344,8 @@ bool ScriptEngineV8::castValueToVariant(const V8ScriptValue& v8Val, QVariant& de
     if (demarshalFunc) {
         dest = QVariant(destTypeId, static_cast<void*>(NULL));
         ScriptValue wrappedVal(new ScriptValueV8Wrapper(this, v8Val));
+        Q_ASSERT(dest.constData() != nullptr);
+        //V8TODO: Data should never be written to dest.constData() according to Qt documentation.
         bool success = demarshalFunc(wrappedVal, const_cast<void*>(dest.constData()));
         if(!success) dest = QVariant();
         return success;
@@ -689,6 +691,7 @@ V8ScriptValue ScriptEngineV8::castVariantToValue(const QVariant& val) {
         _customTypeProtect.unlock();
     }
     if (marshalFunc) {
+        Q_ASSERT(val.constData() != nullptr);
         ScriptValue wrappedVal = marshalFunc(this, val.constData());
         return ScriptValueV8Wrapper::fullUnwrap(this, wrappedVal);
     }
diff --git a/libraries/script-engine/src/v8/ScriptObjectV8Proxy.cpp b/libraries/script-engine/src/v8/ScriptObjectV8Proxy.cpp
index 2cb627370f..ac1fb6f77b 100644
--- a/libraries/script-engine/src/v8/ScriptObjectV8Proxy.cpp
+++ b/libraries/script-engine/src/v8/ScriptObjectV8Proxy.cpp
@@ -1087,6 +1087,8 @@ int ScriptSignalV8Proxy::qt_metacall(QMetaObject::Call call, int id, void** argu
         connections = _connections;
     });*/
 
+    // V8TODO: this may cause deadlocks on connect/disconnect, so the connect/disconnect procedure needs to be reworked.
+    // It should probably add events to a separate list that would be processed before and after all the events for the signal.
     withReadLock([&]{
         //for (ConnectionList::iterator iter = connections.begin(); iter != connections.end(); ++iter) {
         for (ConnectionList::iterator iter = _connections.begin(); iter != _connections.end(); ++iter) {
@@ -1099,7 +1101,11 @@ int ScriptSignalV8Proxy::qt_metacall(QMetaObject::Call call, int id, void** argu
 
                 Q_ASSERT(!conn.callback.get().IsEmpty());
                 Q_ASSERT(!conn.callback.get()->IsUndefined());
-                Q_ASSERT(!conn.callback.get()->IsNull());
+                if(conn.callback.get()->IsNull()) {
+                    qDebug() << "ScriptSignalV8Proxy::qt_metacall: Connection callback is Null";
+                    _engine->popContext();
+                    continue;
+                }
                 if (!conn.callback.get()->IsFunction()) {
                     auto stringV8 = conn.callback.get()->ToDetailString(functionContext).ToLocalChecked();
                     QString error = *v8::String::Utf8Value(_engine->getIsolate(), stringV8);