I have a 13 year old QH mare. She nips when I cinch her up. There isn't anything pinching her. Any ideas about what I can try? Also when I ride her she always runs into the shelter and stops. What am I doing wrong? She will either run into the lean-to or the side of the shed and just stop. She goes from a walk to a trot to a dead stop and she won't respond when I pull back on the reins or try to turn her. I use a snaffle bit. Help!?