I have a coloured gelding, rising four, on my yard that I ride twice a week to keep his schooling up while he mostly does lead rein rest of the week. He was originally broken in to compete in working hunter, show jumping, xc and dressage. But plans didn't go to plan and he ended up being a lead rein pony for the time being. At first he was foot perfect, he was figuring out ground poles, how to extend his trot, pick the right leg up in his canter transition and all that fancy stuff. But as soon as he got a taste for lead rein, he'd turned into a complete devil. He now bucks, spins, rears and bolts off lead rein, won't accept a contact, doesn't want to go forward, then doesn't want to stop. Lead rein was quickly stopped because his owner thought it was a health issue. Backed was checked, saddle checked, his feet, he got a lame test and scoped for ulcers. Everything comes back fine. He's 100% okay to continue. So he's put back into work, he's still an arsehole off lead rein, decided to try him on lead rein with a teenager riding so if he acts up, she could sit and circle him. And he's back to being foot perfect, There isn't much difference in the work load, his still does walk, trot and canter on lead rein (his owner can somehow run to his canter) Pony is 12.2hh so he isn't massive. But it's becoming a pain in the backside when I'm trying to school him. Is there any reason why this can happen?