I have checked out an EASI reach truck for limited traction speed and found that the truck needs a new forward/reverse potentiometer. I also noticed that the read out beeps and flashes "lift?" when keyed up. I have lost lift all together and have a code 21 show up once in a while. I tried to install a replacement pot today but the pot is also faulty. If I try to activate lift when the display shows "lift?" then the lift motor flashes up momentarily, stops and won't lift