Can't tie leads to (stone) walls. At first i could tie the horse to my stone walls that surround my shack. After i went somewhere with my horse and i tried tying him it didn't work. The only thing that could cause this is the fact that I didn't unleash the horse before riding him but instead i broke the leash while riding the horse and after that it didn't work. A while later i could tie my horse to the wall and then i left again the same way breaking the leash and i couldnt tie it again though i didn't test unleashing the horse riding it and then tying it again.