Menus suddenly go blank
I was using Preview for a while and suddenly, all menus from right clicking menus, the top bar, and pop up menus for logging out and shutting down went completely blank. They go back to normal after restarting and logging out and logging back in. I've been told it might be due to an overload in the system, but it sounds kinda unlikely since it was just Preview. Does anyone know why this happens?
MacBook Pro (Retina, 13-inch,Early 2015), iOS 10.1.1