Exmark laser hp 52" working when parked. Go to use it the next day started up fine went to disengage break and wanted to stall I hurry up and get a break and stayed running fine. I bypass all safety switches(seat,brake,2 control arm,tilt) and now when I engage the PTO it goes to stall shut it off and it stay running. I replaced the seat and the brake switches and the results were the same. went over all wiring to