Flipping over when saddled and pulling back when tied

Question
Hello my name is Summer and I have a 10 year old quarter horse On The Money Redneck. He is a gelding and he is in 24 hour pasture turnout with many other horse buddies large water toughs, grass, hay and mineral blocks. He is a beautiful horse and very well built and bred. The only problem was he was previously foundered and I was told from his last owners that the owners before them abused him while he was tied to a trailer once and caused him to flip over and knock himself unconcious. He is not my first horse and I have trained before but never one with his problem. He was foundered but his feet are healing and he is comfortably ridden in a hoof boot. The first couple of times I rode him he was fine but recently the last two time I saddled him he flipped completely over. It was out of nowhere and I almost didnt see it coming. I had just got done saddling him and his eyes got real wide and he started breathing funny and he got really still. Then all the sudden he went to lay down, got up and reared and then flipped completely over and rolled and ran off. I caught him and calmed him down. He wasnt hurt and seemed fine so I resumed the ride. He did great. The next day I had no trouble but the day after that he did the same thing. This time I saddled without him being tied but my friend was holding him and he reared up, flipped over and ran off. He has been vet checked and nothing was found. No lameness or soreness that would cause the behavior. I am wondering if it is because he is scared or doesnt want to ride. I am having my chiropractor adjust him tomorrow. I dont know wether to punish him if maybe he isnt wanting to ride but I dont want to punish him if it is fear of what happened before. After that when I rode him he seemed a little worked up and bucked a tiny bit so I longed him first and then he was fine but this time he had landed on gravel so he cut himself up a little bit. I am worried as this is such a dangerous habit and I fear he may do this one day while I am riding him. Also he rears and fights being wormed but puts his head down and opens his mouth for a bit. He is a very sweet horse and I dont want to have to get rid of him. My dream would be to fix him and maybe barrel race him because it is what he is bred for and he seems to enjoy it but I have to get him over this first. Can you please help me? Any suggestions are greatly appreciated!

Answer
Hi Summer!

My only and final advice is to stop riding him immediately, remove him from any riding with anyone ever again and retire him to a pasture to be a buddy to someone.  Do not sell him or give him to anyone you even suspect might attempt to ride him.  He will hurt someone, as sure as the sun rises. If you sell him failing to disclose this issue or give him away knowing he does this, it could come back to haunt you with a lawsuit.

My only concern is the safety of the horse and human.  This extremely dangerous and irrational issue your gelding has will never be fixed, not by you or any professional trainer.  Love, time, discipline, beatings or training will not cure this issue.

Anything with a brain can be "wired wrong" and then we see issues like this.  Your gelding could not be telling you more plainly he is not a trustworthy riding partner...unless he spoke the words out loud.

Use your head and not your heart on this and retire him to be a happier and safe horse.

Solange