Very difficult for propane combustion gasses to get inside an RV via the water heater.
Combustion/exhaust chamber goes inside the tank which is FULL of water.
So propane combustion gasses have to be coming in thru window or vent (opening ABOVE the water heater)
That also would require poor propane combustion......orange flame, obstructed combustion/exhaust chamber, some sooting etc.
Sounds like you should do a complete burner cleaning
Pull burner tube....clean it out using small bottle brush
Remove gas valve MAIN Orifice---soak in alcohol then blow out with air pressure (don't stick anything thru orifice it is a precision hole)
Remove spark electrode & assembly---clean high tension wire contacts, clean electrode (emery cloth) and clean mounting screw area (ground source)
Clean combustion/exhaust chamber----run wire thru, tie rag to wire thru pull it back thru chamber
Reassemble and fire off.....check flame. Should be strong steady and BLUE