I apologize for not reading all the posts but the more I think about what the vet said regarding "being lazy" the madder I got
1. The first I'd do is, by all means, find a new vet.
1. The second FIRST thing I would do is to locate a qualified chiropractor.
2. My Arab will drag his back toes when his ancient vertebra injury starts bothering him a lot.
3. The horse is in obvious discomfort for either one or several reasons.
3.1 Regardless of how "wrong" the equipment and/or the rider is, the horse should not be walking on it's toes in the back (OP said that a few posts back).
3.2 I would check very thoroughly for deep thrush. It's possible the horse can have thrush and walk ok at liberty but not under saddle.
3.3 I might try riding this horse bareback and with only a halter, in an enclosed area. Get pictures to see if the head/neck/back set are any different. Also check to see if the horse still lands on its toes.
There is no doubt this horse is uncomfortable - it's going to take process of elimination to figure that out.
One thing for sure, it is NOT a healthy sign the horse is landing on its back toes
That has not one thing to do with being lazy ---- blessssssthevetsharrrrttttt-------------