I am doing some character animation in Flash CS5.5. During a slow breathe cycle (breathe in and out) the legs and arms are jittering. I have them set on a motion tween with a custom ease in and out. Somehow the head and neck and torso are not affected. Frame rate is not the issue, I've changed it around and anyway we have to stick to 24 fps to keep consistent with the style of the project.
In the past when I've run into this I've been able to reset the motion tween or change the angle the symbols are moving at to fix it. I've also tried dragging another frame from the same layer over to replace the glitchy frame....sometimes those things help. Sometimes resetting the anchor point helps. But I've tried all that and I still run into this problem. Removing the eases doesn't help either.
slow mo jittering in Tweens is unavoidable, since Flash will always round intermediiate values awkwardly (in a "fast" anuimation part you simply don`t recognize this)
You could convert this specific tween to single keyframes and stick to pixel perfection (only use whole-number values for your sprites positioning)