I haven't quite paid enough attention to AR's form and fundamentals but I would guess that maybe in trying to mold AR into a better QB, the training inhibits his natural athletiscim and instincts and in trying to be a better 'pro' quarterback by not doing what he's always done it created major frustration for him.
Like instead of rolling out, throwing incorrectly, having his feet wrong, etc; which may have worked, that internal training of 'dont throw this way, stand this way... ' may have been a huge frustration. Whereas doing things the 'wrong' way worked for him and doing things the 'right' was wasn't working. I think we can all relate to that.
It's like when your boss comes by and your like 'oh yeah we always do it this way' and then your behind the rest of the day because it took so long to do things the 'right' way.