Bob,
From reading all the info you have provided, the issue is only when you are in transit. That being said, you are losing air somewhere in the rear leveling system on the drivers side. The ride height valves in the rear control the side to side leveling when in transit. I would look for an air leak at the drivers side rear height control valve, air bags and related air hoses or the HWH 6 pack solenoid block that controls leveling when parked and ride height when in transit. Extreme caution is required while being under your coach! Here is a pic of the HWH 6 pack so you know what you are looking for. Hope this helps, Fred