i Have ipad Air and when i call facetime to ipad air 2, it not work as smooth with ipad3 (new ipad 3.3)

i Have ipad Air and when i call facetime to ipad air 2, it not work as smooth with ipad3 (new ipad 3.3), it freezes or hang a lot and when it sync all what happened on freeze time, all movements goes very fast for a second and it not sync with voice.

Is this a common problem, or is it a new kind of problem?.

iPad Air using iOS 9.1 beta4 and iPad Air 2 using iOS 9.04

i know that because i use beta, it can be the problem but why it not have this problem on other iDevices, just iPad Air 2?