I have a ZD221 48 zero turn and constantly have starting problems. If you get off mower to pick up stick it will shut off even with parking brake set and not restart. Three times I have dismantled and removed the switches and no problem all function well. I crank it and make the safety switch cut it off by releasing the brake and lift off seat or other maneuver to make it shut off. It functions fine a couple of times then wont start. Anyone have a clue please help me, just cant find problem. Once it gets warm and runs for a while and you shut it off it won't start.