QPushButton hover enter event not always happen in QGraphicsView when it is resized

I have a MainWindow, inside it i have QGraphicsView and inside it i have one QWidget with two buttons.
In default state of the window(1024x726) i don't have problems.
But when i resized the window with size which is more than 2 times bigger from the default one, from time to time i don't receive HoverEnter event on my QPushButton ( style for hover is not happen, mouse cursor is not changed ). But when i move the mouse outside of the button i receive HoverLeave event.
On the first screenshot, my app is in default size -> everything is fine.
On the second one it is resized, my mouse is hover Button2, and mouse hover event is not received.
The source is attached too.