To me he looks unbalanced and overflexed. I'm not sure how much is the rider's fault, she looks like she's really having to drive him hard at the canter to keep him from falling apart. Looks to me like he'd take quite a bit of flat work to correct. Not that that's impossible, but I don't know how your pony compares, whether it would be a fair trade or whether you'd be getting the short end of the stick.
Do you have any confo pics? His confo will have a lot to do with his potential ability as well.
I agree with Apachie, and add that he needs some serious work on transitions. He was strung out on every one. I think the head tossing is his evade-the-bit method of choice, and when it's harder, like at the trot, he goes behind the bit.
Did they have video of him going to the right too? I'd say definitely ride him yourself, or ask your trainer to, to figure out if it's horse or rider. Good luck!
The video is too far away to see how the rider is contacting his mouth, or any details of conformation. I like this horse, nonetheless. He is fairly forward and rythmic . The transitions were very sudden and not pretty but I get the feeling it's something to do with his relationship to the bit. Either he has some discomfort or has a memory of it that makes him not want to come to and stay there. The rider was ok, though she was a bit passive. The hrose stepped under himself well and had a lot more to give at the canter than he was giving but I like the amount of suspension he had.
She let him spend too much time behind the vertical and if that has been his way of going for a long time, you'd have some work to do to erease that.