Zombie gets stuck attacking walls or even thin air. I have seen them do this when they miss an attack on me, they continue to attack "nothing" forever. If I was the last thing they hit, then they continue to hit me no matter how far away I get from them. If they were stuck in the animation already and I don't go near to them, then they will not hit me. If I get caught in a hit from them then they do what I described earlier, continue to be able to hit me no matter how far away I get.