Probably worth having a specialist instructor give you a lesson on this horse - probably is your technique and your other mounts maybe used to it!! My pony requires a very very strong contact to keep his brain in gear when attacking jumps, he gets so excited that he runs out or on or bolts with glee!! It may just be that this horse is not quite collected up enough on the approach and is coming apart as he(?) goes over. Impulsion may not be quite right, you may be a little to forward when landing, all sorts of posible causes. As i said best cure professional lesson. Good luck
