TBC Quirk - Menu Exapnds on Opposite side

I was scratching my head at this this morning. Just odd.

Probably because it is more than 50% of the way across your screen or some internal settinh like
That. If you use the TBC standard menus or create a custom menu and move a command in a menu it may act differently to deleting the menu item and adding it back in as a custom menu addition

Not sure what else it could be