I had no issues at all for 3 years and suddenly Kiara the paint started to poop in water bucket in stall. Moreover when we moved it so it wouldn't be too convenient for her to do she pooped in hay bucket (I keep big "muck"-type bucket for the hay attached to the wall instead of throwing it on floor or in hay rack). And I mean she INTENTIONALLY used it for poop. All hay is gone, no poop in stall on floor, but a HUGE pile in hay bucket. What could be the reason for doing that?