Before condemning the joystick itself there is a troubleshooting procedure to go through to ensure that there is no wiring fault, etc. See the attached. You are welcome to a complete electrical schematic for the machine but that will require a machine Serial Number (last 8 characters of the 17-character PIN) to identify the correct one. There are 15 different models of 120M so it's important to get the correct info. How many total hours on the machine.? The mechanical parts of the sensor assembly may be getting worn by this point.