Are you doing every single frame? Or are u key framing one frame, then skipping ahead a few frames and adding another key frame? That’s the only way I can see it going in and out of sync like that.
But if you go through frame by frame and add a key frame for every one, there really isn’t any way I can think of that it should go in and out of sync in the way you describe.
Could it possibly be messing up because of my settings, or something else I am doing. Could it be that each frame isn’t loading properly and I’m not masking in the right positions? I am completely lost! 😦