QQuickWindow sometimes produces white flickers when resized

See the attached sample project.

It will create multiple windows, that are resized every 500ms. Some of them will show a white flicker when resized (If it is not showing the flickering increase the window count)

To prevent the flickering uncomment the two lines marked in "TestWindow.cpp"

It will cause the background of the window to be transparent, but the scenegraph is not affected by this change, the black rectangle defined in "main.qml" is still black.

But I'm not sure what downside this "fix" has, maybe somebody can elaborate.