Any horse person can tell you stories about a horse that just seemed to take a dislike to somebody. There's a nice TB mare in my trainer's barn, she goes well for almost everybody, but she took an instant dislike to me and will not go well for me. We just got crossways with each other from the start and did not get along, I don't know if it's something I did (the way I sit, my hands, my aids) or if she just doesn't like my looks. Sometimes (like with people), it's just a personality conflict and that's that.
Thanks for sharing.