This hyster s155ft lp gas keeps shutting down with no codes. I can't get it to do it for me but the operators say it does it when they switch gears while keeping the Rpms up and left foot braking. I also seen it happen when they left foot brake and hold the rpms up as they go in for a lift and as soon as they lift or tilt it shuts down. Starts right back every time. I've combed through the harness and haven't found bring that sticks out. Brand new motor. I have no clue what it could be. It sounds like it could be a short but I can't find anything. Could it be the hydraulic control valve? Desperate for solution. I'm under a lot of pressure to get it fixed. Thank you for taking the time to help.