Check all your hydraulic hoses to the mast from control valves. If you have extra play with the controls check the little cup things under the control valves and make sure they are still connected. I had one lift that would drop loads but raising load was fine. One of the lil cups had come loose allowing down valve to drop freely. Also seat switch could be faulty. Had one where you sit down switch is activated and go to drive and the switch deactivated without shifting of the body. Also check all you position sensors on the lift. Hopefully something helps