My horse was a hot mess when I got him, but he is a lot better. His neck isn't so upside down, he holds his head low, is giving to the bit, very willing etc. the only problem is cantering. Now before I describe the problem, know that I am a good rider with a trainer, and plenty of experience. This horse is a Spanish Arabian (or that's what his owners told me... I can see lots of Arabian but I see some foundation quarter horse, big muscular butt, shorter legs, but Arab movment) and is never ending energy, very intelligent and VERY easily bored. He was not only gelded late, he had horrible training.
He has made massive progress, but he runs off in the canter ONLY in the arena. I ask (gently, he moves great off leg pressure) and he freaks. He runs into it, then try's to gallop off into the wild blue yonder. After a few minutes of this, be kinda centers himself and is easier to control. He is heavy in my hands when he does this, and very hard to stop or slow down. At first I thought pain, buts that's ruled out. Then I thought it was fear. Also ruled out. Then I thought serious rider error. I'm not the best, but once again ruled out. He has NO balance in th canter, and no idea how to find it. He falls in on turns and just goes faster and faster. I have tried to do downward transitions from the canter, but he just melts into a jittery, hot mess. I heard that lunging on a hill might help.
And PLEASE, before you respond telling me I'm awful, my horse needs a new owner, or he is not the right horse for me, just try to remember how much progress he as made. He no longer bucks, rears, randomly bolts through solid objects, kicks, bites, rolls, and he can now w/t on a loose rein reliably, with good quality of movement. He is unrecognizable compared to before I got him.