Maybe I'm missing something. Bob stated that the problem only occurs when he is driving the coach. It maintains level when static, both in travel and level modes. So it would seem that he's not going to find any air leak when under the coach if it is sitting still as apparently the leak only occurs when road vibration is also present. If the preceding is accurate, IMHO his best bet is to take it to a shop that has a lift as I would be very hesitant to attempt to initiate an air leak in the leveling system while under the coach. His other option is to throw parts at it in hopes he'll find the leak.
Steve