Dragging dock widgets with grouped dragging feature is buggy. Playing around with widgets using examples ends with missing buttons, invisible widgets.

In my application, which code unfortunatelly I cannot attach, after few drags to undocked window strange empty rectangle is shown in the main window.

On attached screenshots (1 and 2) there are windows with missing buttons.

On 3 there's a checkmark next to the blue widget, but it actually isn't visible anywhere on my screen.

On 4 there's a strange gray rectangle on the left of the main window. After few drags, everything crashes.