I am not new to barrel racing. I have trained up and sold off a lot of nice horses. This guy has me "face palming" far too much. 14 year old gelding that I've had for about 4 years. He was a ranch horse that I purchased out of the "Legacy Horse Sale" for those who are familiar in Arizona. He is fancy broke. Extremely smart and extremely quick. He is quirky. If he gets ahead of himself, he gets panicky. Lacks confidence.  But by gosh, he took to barrels like the snap of a finger. I've been running him for the past 3.5 years. Not super consistently all that time. Maybe 2 races a month during the summer. 3 if I got lucky with my work schedule. 

We were clocking decent 2D times. Some 1D. Now, suddenly, one race he will run a beautiful pattern. The next, he will turn first and run sideways back to the gate. I can't figure out why. He's been treated for ulcers. Had teeth floated. Had a lameness exam done. He gets chiropractic work every couple months. I have used 2 different chiros in hopes that maybe one will find something. But they both say he checks out great. He's never bled, however not been scoped. Doesn't ever cough after a run. No gate sourness.

I have no way of anticipating this behavior, so not sure how to go about correcting it. He doesn't do it unless we are running. So, I could potentially just lope to first, and run the rest. But... that's not really using full potential. 

I was thinking a possible bit change ( I know bits aren't a fix, but maybe it is what he needs). Currently in a Sherry Cervi twisted wire dog bone. Have used a Connie combs mullen mouth stabilizer when he was getting super noodley. 

Looking for your thoughts and opinions. 

Thank you.

Most likely, sore. Lots of times when they do that it's a front foot or soft tissue (like suspensory) in a front leg. Soft tissue a lot of times won't show up in a lameness exam, it's found by ultrasound.

My horse will do the exact same thing if he is hurting somewhere.

I agree on the hurting somewhere... 

What happens if you change direction to the first... go left first instead of right, or vise versa?

I had one like this, not a thing wrong with him physically he just hated being a barrel horse. He'd make 2 decent runs and the 3rd take the bit and run off on 1st. He's now a ranch horse and excellent at his job. 

I try not to be a pessimist, but everything you described sounds like a bleeder to me. Mine did the exact same thing for a long time, but it was 2nd barrel. Totally unpredictable at first, but then we both started anticipating it and it made it worse. Finally, about a year later, he bled out his nose and mouth, bad, and all the pieces came together. I'd tried everything, just like you. I gave him a few weeks off and some SMZs, brought him back slow with Lasix, and he's never done it again. To me, it would be worth it to try and see if it helped resolve the issue, then you'd know. Nobody wants a bleeder, but denying it or keeping your head in the sand doesn't help him or you - that's the mistake I made and I wish I could do it all over again. 

ETA - Mine never once refused the gate, or even acted hot at the gate. Would walk in flat footed. Perfect in practice, didn't cough when he came out, in great physical condition. The first time he ducked a barrel, my friend told me he was bleeding and I told her she was nuts. He's not the type you'd expect to be a bleeder, but boy was he. 

Brave enough to post a video??

Of course, general rule of thumb is when a horse doesn't something out of character that doesn't make sense, is there is usually something PAIN related bothering them.

Honestly, I feel that chiro work is important but perhaps I place less weight in it. I had TWO different chiro's miss the fact that my horse had a very serious congential issue with the vertebrae in his neck and/or didn't tell me about it when I specially would ask "what did you find"? It's soured me a bit on chiro work, I guess.

I'd go back to your lameness vet. Sometimes you have to be persistent. Surely something showed up on flexions?

If not, I'd xray hocks and stifles (if you didn't already) just to check. Sometimes they can flex fine and still have issues.

Depending on how much money you want to spend, could also xray front feet and back. And neck. Sometimes you don't know what's there until you look.