>>354702785
When you're in first person it shrinks down the head bone to 0 so it doesn't clip in your view. All your stuff parented to the head bone get fucked by it because the clone that you can see in the mirror and cameras is still somehow affected by this scaling or something. It's local only though because players don't have a mirror clone of anyone but themselves.
Another thing that can fuck it is having multiple things affecting the same movement. Example if you have a rotation constraint and a rotation on a movement it'll be all fucked too but only in mirrors. Pic related had a rotation on an animation and an aim constraint. Works fine looking down but it's fucked in the mirror.