[busboy4]

You know Jerry, it could be your vehicle height sensor. That is the shock absorber looking sensor visible on the rear of the rear axle. Perhaps your bouncing it and putting it up and down the lift exercised it toward its extremes and (for lack of a better explaination) loosened it up. I cannot necessarily reconcile that idea to your finding that the system leaked down even with the switch off, but at this point it seems very hard to pinpoint a problem. I don't think your air suspension warning light is on, so the system has not sensed a failure, but a malfunctioning, yet operating sensor might cause the intermittent problem. Just grasping here mind you, but the height sensor is what tells the solenoid valves to open/close and the system to inflate/vent. So, perhaps it is giving occasionally erroneous readings.
Keep us posted.