Adding a QGraphicsProxyWidget to scene causes QGraphicsItem with a child QGraphicsProxywidget to paint incorrectly

Create a simple QGraphicsItem with a child QGraphicsProxyWidget.
And add this to scene. No problem till here.
If you add another QGraphicsProxyWidget into the scene, painting of the previous QGraphicsItem messes up.

The attached test code works correctly on Qt5.6 but not on Qt5.7. When you move the splitter left&right you will see the error