In the attached example, click on the "open dialog" button. After dialog opens, its buttons do not highlight when moving mouse over them. If you close the dialog by keyboard or by clicking the "X" button, the "open dialog" button now does not respond to mouse over, too. After you click somewhere inside the window or dialog, everything works fine.
In this example, I could open the dialog in response to clicked signal of the button instead of pressed signal, but we experience the same issue with our real-world application when opening a dialog in reaction to double-click event.