make sure you have the horse placed, and responding to anything you ask him to do,change leads and rythm as much as you can, sometimes they just get bored and they dont care anymore. dont jump to often either, once a week is good enough, you need to work more on flat. you might want to think about your position, usually a horse that hit the obstacle is because the rider will have a wrong position too much in the front, too much in the back, pulling on the reins,reins too short or too long, legs not there, you need to be there 125%, you need to have your horse responding to you.
probably dont jump him for a week or two. and then, you can try free run in an arena, see his reaction, if he keeps hitting, stop jumping for longer... if that horse could jump before he might have been 'digusted' by jumping having done it too many times.