Have you checked the valve? With a pressure gauge on the valve, turn the power off and close the shut off valve to the jack. Are you losing pressure? When the unit is trying to warm the oil, could the car be drifting down? If you feather the manual lowering will it fail and give you the same faults? What about re-leveling? Is it always at the bottom floor?
Johnjays first post was pointing in this direction. I seem to remember this type of trouble. Just wish my memories were clearer.
Also worth noting, the Siemens starter board has a very short life span. I give those boards to service guys as soon as I get them, the 7-8 normally closed ready, and 9-10 normally open ready fail. TKE used to repair them, bad resistor if I remember correctly, but has found its actually just cheaper to swap for new.
Holler back if this didn't help you get on the right page to fix it, I am on TAC 32's now for new installs, but I can swing by an old 20 and look some stuff up if you need it.
Forgot to ask, does this elevator have UPS for the battery backup? I have heard of a few ghost faults when these batteries begin to go bad.