Defense playing wrong coverage in Franchise

I have consistently watched my AI defenders play man coverage when I have selected a zone coverage scheme.  This usually leads to any QB running for 20+ yards because the middle of the field is wide open.  

I've also had guys just completely run away from their assignment in man coverage leaving an open receiver for huge plays.  No matter how good my defense is it is consistently number 32 against the pass and the only way to have a team pass allowed under 300 yards in a game is to get 10+ sacks.