Happened to me after being KO'd by a zombie while stuck in the eating animation. Slid down a hill and slid along a fence. Risked a relog, which seemed to fix the issue. Obviously this would not be something you could/should do in combat with a player however. Perhaps rather than sticking the player in a frozen animation, maybe make them a ragdoll whilst unconscious? Would be slightly more realistic and any movements would then be physics related or a result of desynch on the observer's end.