My horse will jump show jumps in our sand ring fine, no problems, but when i take him hunting he wont jump anything, he just goes up to the jump and gets slower and slower then stops, THIS ONLY HAPPENS OUT HUNTING. Please has someone got some advice, its almost like he just wont pick his feet up out hunting, PLEASE,PLEASE,PLEASE someone help, hes only a baby hes 5 and he used to be good but strangely hes stopped.