I don't think you're spur is hitting him every stride, but you do have some lower leg movment. possibley turn your toes a tiny bit more forward?
in any case, I think he is still a wee bit off, in the hind, not sure which. but he seems to drag his left hind, and it could be that the discomfort has more to do with the tails swishing than anything with the rider (who is actually pretty steady and sympathetic seat/hands).
what happens if you areally ask him to trot out faster, and canter faster? does he seem irritated, or does he perk up and move smoother?