Mouse interaction of QQuickWidget is very slow

How to reproduce this issue:

1. Build the attached example and open it in eglfs
2. Click on "Menu" and select "New QQuickWidget"
3. Try to move your mouse above both of the widgets

Result:

The first QQuickWidget (which was created by default with the main window) works good. The second one (which was created by the user via the menu) has problems with the mouse: movement above this widget is really slow. If you hardcode two or more default widgets into the application, they are working good and only the dynamically created widgets are problematic.

As far as I can see the mouse events of the erroneous widgets are catched by the offscreen windows, while in the other cases the events are going directly to the QQuickWidget.