With the rebar menu on, click the button for the File menu.

Move your mouse to the Edit button so the Edit menu appears, and the File menu button's border remains raised.

I have spent many many many hours hunting for the cause of this bug, i have no idea why it does that

Actually, this bug affects any menu. Start by clicking on the "Help" menu and work your way back to the left. You'll see that the "Help" menu stays raised until you click off the menus. So, this isn't specific to the File menu.

Andrew