QWebEngineView behaves odd when used inside a QDockWidget

[huxol]

We have a central widget which does some heavy rendering using DirectX. I have tried to replace WebKit with the new WebEngine when I hit the following problem. There is a QDockWidget with a QWebEngineView inside that simply loads some web pages. As long as it remains undocked, everything works as expected. After docking it becomes really sluggish. Highlighting during MouseOver, inputting text, clicking links, everything gets slow. It seems that the QWebEngineView or the QDockWidget are not getting updated correctly. When I stop the rendering, or when I add a QTimer to the DockWidget which calls update() frequently, everything works as expected. Is there any way or place where I could start look what the actual problem is?