Roger has outlined a few good things here worth looking at, a little closer. In his earlier posting, he focused on possible multiple issues that could be passing along problems for you.
On the other hand, that/those coaches that remarked about your release point, should be addressing your “pitching cycle” in total. Why? Because each phase of your pitch cycle contributes to – or not – the next phase in your pitching composition. Your relases is really a phase of continuance, not just one point or action in time.
Go back and ask this/these coaches how to correct the issues that you’re having, instead of drawing their attention, then leaving you to figure things out for yourself.
This media, as usefull as it is, has tremendous limitations when addressing your question(s). Even when posting video of yourself. In real time, being “there” right with you, step by step, is the only way to truly adderss a correct course of action that wlll benefit you in the long run.
So, if a coach tells you sometihng is not what it should be – STOP, ask him to explain in detail, even show you in real time what’s what, then work with him to get it right.