My BO has a stall kicker. She kicks the wall so hard I cringe, one of these days I imagine she will break a leg. Her owner thinks chains, shock collars, etc are cruel. In her case it’s a territorial thing. No other horse can be moving, though, and she will just WHAM when she feels like it. No advice here as I feel you have already been given a couple of good options to try, just sympathy from me!
It’s about 10 years later, but the OP still has this mule and he is no longer a kicker, in fact when I pointed this thread out to her she couldn’t remember him ever having been a kicker at all.
I know this thread is old, but a cheapo suggestion that has worked at our barn -
Hang old feed bags from the walls. They don’t like the sound or texture of kicking a crunchy feed bag, and quit pretty fast.
