Yes! I'm having the same issues with my horses. It's the main reason I'm using the teleport cheat to move the horse and rider to the competition rabbit hole at least an hour before and queueing up the brushing, cleaning, etc. Sometimes an hour and a half. I'm going to remove the horseballs today and see if that has any effect. Well, it won't be today because the two oldest boys are at university, but when I'm back in the town, I'll try that. It's not just you. Although foals don't seem to have this problem.