Thanks for the info!
Just to be clear, the kitchen, bathroom, and bedroom are fed by a single square duct that runs under the floor. That square duct is fed from one round duct that comes out the furnace. As you mentioned, there is another round duct that feeds the living room. Out of the furnace there are 3 other rounds ducts and I have no idea where they are going or what it's all about?
Speaking of the square duct, at one point we had practically no air coming out of the bathroom and bedroom ducts. I removed the vent covers and using a mirror and flashlight and checked the duct. All seemed good, and could not figure out what was wrong. So I then asked my wife to start the furnace while I was looking in the duct. Sure enough, the duct was obstructed by a piece of foil inside the duct that got loose and basically acted like a valve and stopped the air flow. Finally we were getting somewhere, now the trick was to remove that loose piece which was located about halfway between the kitchen and bathroom vents, almost inaccessible. It took about an hour or so with a stiff wire to pull that piece out.
Is your 5th-wheel skirted? Mine is not, we are going through propane much faster than you are.
2016 Silverado High Country 3500 Dually Diesel 4x4