So this is a new issue for my horse and I'm not sure why he is doing this or how to fix the problem. I have a 15 yr old TB gelding and a miniature mare that cannot be separated. They are at their happiest when they are working together so I always free longe them together in the indoor arena. My TB likes to work and he is usually a complete gentleman. Lately he has been clearing the arena fence while longeing only to stand there and wait to be let back in. I have seen him do this when I leave the mini in the paddock but lately he is doing it even when she is with him. He doesn't seem like he is unhappy or unwilling to work when he hops the fence, it's almost like he just gets excited and wants to show it.
Background info: at one point I was schooling him over fences until I learned that he had a broken tibia in his youth, ending with him having 3 pins in his leg (not disclosed when I bought him) and I stopped jumping him for fear of reinjury.
Why could he be acting like this? What can I do?