Sooooo, one of the things that the RV dealer supposedly did for me was to sell me and install tire air valve extensions. 
These snazzy little hoses and such make it easier to be able to check the tire air pressure, especially for the inside rear dually.
He told me that when I brought it in for the trailer light controller, that the inside road-side tire was leaking air from the valve stem. So I told them to replace the extender or stem that was leaking and decided it would be a wise investment for me to purchase one of the TPMS (Tire Pressure Monitoring System)s. This allows the driver to get a real-time digital readout of the individual tire pressure(s) and temperature.
I got the coach back from the repair shop yesterday, and the TPMS I ordered from Amazon arrived today. I successfully programmed the system, installed all the sensors on all six tires and “VOILA” the little LCD monitor screen showed all the tire pressures and temps. AND GUESS WHAT ELSE? The road-side inside tire had NO AIR IN IT!!!!
So glad I bought this system because there’s no way I would have known that tire was empty and, having been told by the repair shop all was good and that they had filled all the tires to 105 psi, we would be heading out Saturday morning with a flat (and dangerous) tire.
The coach has an on-board air compressor for the air brakes and the air suspension, so tonight I pulled out the hose and tried putting air in the tire. I only heard air leaking out the back side, not sure if it’s a bad rim/tire seal or bad valve stem or stem extender.
But guess where it’s heading first thing in the morning? Back to Galion (again).
