I'm servicing the above lift- unit has a strange symptom- hydrauics work good until you turn the engine off. Once restarted, hydraulics take about 1 minute to come back to life. If you leave the forks up when you shut down the engine, lowering the forks will immediately bring the hydraulics to life. Once working, the hydraulics are strong with no aeration of the oil in the tank. Any input would be appreciated