Sound intermentently doesn't play with Apollo

why does sound still drop out intermittently with the Apollo and Nuendo? When you load projects into Nuendo while using the Apollo often times when you hit play no sound will play. Or when you load UA plugins the audio will stop… When you try to reset of close out the program it freezes and you have to force quit. But when I hook my other boxes up I never have this issue… Been making this complaint to tech support I was hopping this would be fixed with this version. Anybody else having this issue?