fongka2 , i think Ashley should decide that, not you.
vagaev , i noticed something similar, a long time ago, that only happens if the animation speed of a sprite is higher then your fps/2.5 .
You should definetely post a capx, where you show that, else Ashley will most likely close it,
it may be a bug, may not, Ashley probably has a explanation why that happens ready
How im handling it: If animation Speed != fps/2.5 - set animation speed to fps/2.5 (That way i keep it with 60 fps at a 24 playback rate, (pretty smooth))