When Window has no activeFocus, activeFocus lost after transitioning back from Dialog to Window

Please refer to the attached sample,
where it tries to make a Dialog visible after 2 second and hides after again 2 second.
So, after 4 seconds, the active focus is set back to the StackView and Rectangle as expected.
But if another window is selected before the 4 seconds, the activeFocus is lost and never given back to the StackView and Rectangle.