How steep is the hill? He may have have to tighten up the snubber,or adjust whatever he has to control the ammount of force it takes to activate them. We could back ours up small to mild hills pretty easily, but on steep ones we still had trouble, even when set where it was supposed to be. So we drilled another hole in the coupler where it slides to push the piston back, and if the hill we had to back up was to steep, we could stick a trailer pin in it and it would lock the brakes in the dissengaged position. Worked really well, and is hard to describe without pictures.