Well I wish I could offer better support. But right now the big problem is Ludie(CJS team) doesn't effectivly communicate changes to the code. This often leaves Ahsley having to muddle through the Physics errors through different releases.
Report your bugs with a super simple capx(makre sure to see if the bug is reported) and hope that the next 1/2 C2 beta releases fix the problem.
The other solution in the mean time. Is to not use Physics. Actually in fact my game wiched used physics only for flight I had to remove.
Also Physics is cool but sometimes Physics is often over used. How much is your physics needed. Often if you need to simulate accurate falling blocks is the the only time. If your using physics just make objects fall easier then you can work around that. Both Platformer and Bullet offer Gravity and the ability set Gravity levels.