George,
Your airbag most likely has a small leak, or the air line to it is leaking. There is only one front ride height leveling valve, so don’t think the valve is the problem or both front air bags would be leaking air. One other thing, do you have the SMC hydraulic leveling or air leveling? If air leveling, then your problem could be in the air solenoid block that controls the leveling system. Need to get some soapy water and spray all the components to determine where leak is originating from. Not easy but doable. If not comfortable getting under coach, then take it to a professional. Hope this helps.
