My father bought a AQHA gelding back in 2012 Diamond was rode only about twice a year as a trail horse. I got Diamond and started working with him in early 2018, after getting him I noticed a problem where he would completely refuse that left lead. I would put him in the correct position and most the time he would just quickly shift out of the position and take the right lead instead. Only once out of six times would he ever take that left lead. I decided to focus on building muscles by working with him at the walk and trot. After getting the trot down I had his back adjusted and I started to work with him on loping. I worked with him in the round pen. I would ask him to lope and he would refuse that left lead yet he picks up the right lead fine. After awhile of him taking the wrong lead and me stoping him and asking again he started Cross Firing. I called the vet she had me lunge him and she said he has arthritis (Diamond is only 14 years old). I had his hocks injected and after a week I continued to try to get him to lope left lead in the round pen but there was still no change. Figuring he was assuming he was in pain and I needing to focus on other horses, I turned him out for about a month. I recently started working with him again and instead of him never getting that left lead but once in a million times, he gets that left lead but only half way... He cross fires... I love Diamond to death and we have such a special bond, but if it is a health issue I sadly can’t afford to have a vet look into it. I’m really hoping there’s a way to rule this out without a vet bill. How can I fix this disunited canter and why dose he do it? Any answers would be so much appreciated!