Definately helpful to have someone watch from the ground.
Besides tack, the rider, or pain, I just always want to add that he may just be having a regression in learning ... which is somewhat normal!! Sometimes when learning new things, the horse will do awesome for a certain time period, and then all of a sudden act like they never learned it at all. It happens. He'll come back around (provided there not a tack issue, or pain, or a rider issue that is causing it).