WebSockets not working, use of Google Firebase causes render crash

Stesteste

I am trying to connect to Google Firebase from a page I show in a QWebEngineView and the moment the following line is executed, the render process crashes (i.e. renderProcessTerminated is signalled).

var ref = new Firebase("https://my-project.firebaseio.com/");

Also, I cannot establish a WebSocket connection. I get an error that it failed for an unknown reason.

Could these two be connected? I built the webengine from source here. Many things are working alright, e.g. YouTube.

Stesteste

The exit code of the renderer is 3.

Stesteste

Ok, it seems that WebSockets don't work fore me. If I force Firebase to use long-polling via

Firebase.INTERNAL.forceLongPolling();

before creating the Firebase object, then it works.

I have webengine 5.9.1 built against qt 5.6.2. Has anyone tried websockets in this constellation?