Does this bug affect everyone? Try installing said pathetic excuse for a media player, and then in ‘Player Preferences’ untick ‘Show Content Guide at startup’. Exit and reopen the program, then try to maximise or resize it. If you’re getting the same result as me, you’ll know instantly that Apple have screwed this one up pretty badly.
It's mid-November and my annual review of the year is nearly written. So ahead of things. Except presents: not ahead on presents.