I once worked at a place prepping horses where before my ride time, I was told that if I got on and the horse swished it’s tail “at all,” to get off an immediately hand it to the grooms so it could get lunged again. This horse had this particular stop/prop/spin trick that had already gotten several riders off and injured a few. It didn’t pull it with me so I was never nervous, but I could definitely understand why you would be - and I’m sure if I HAD experienced this behavior, I would have been, too.
It’s hard even for a pro to stay on something that truly gives no warning, as some of them do. I feel like this is more of a learned behavior to get out of work than a pain issue, since pain doesn’t really come out of nowhere and unless it’s stopping before a jump because the take off or landing hurts, pain issues tend to have a forward response (i.e. bolting, bucking, etc) or at least building anxiety, and less of an out-of-the-blue stop/spin.
To be more blunt, I wouldn’t deal with this. If the horse was good on the ground, I would donate it someplace where the horse could just walk folks around while being led, or I would retire it. If you sell, you’re putting someone else in harms way and eventually the horse might come to a bad end itself.
