There are internal valves in the pump to control leakage and therefore drive movement, the drive should hold its position, I think the only solution is put everything back the way it was before and correct the external connections as it sounds like the pressure on the 'down' side (now your 'up') isn't sufficient to trim against load and this is because it would normally have gravity assisting when trimming down. you need the high pressure and positive lock on the 'up'side.