3 way Dometic frig works great on shore power and on battery when towing. It is not cooling on propane, or maintaining an already cold frig. The propane setting worked great about 2 months ago. 

Camper is level. 2 burner kitchen stoves burns well with a blue flame. Furnace runs well. We are opening the propane tank slowly once we are parked. 

Original issue was when frig would not switch over to propane, just clicked, wouldn't light.  No visible debris, so we took it in for service. They found a mud wasp (dauber?) nest, but where exactly I don't know.  We brought the camper home, thinking it was fixed. It lit without issue but it did NOT cool, at all.  Back to the service guys, kept it for days, no luck.  We picked it up and tried the following on our own:

Disassembled the burner assembly and cleaned the tiny orifice with iso and air. NO Luck

Replaced the regulator and propane tank. NO luck

Disassembled the burner assembly more thoroughly from the valve connection at the Solenoid to the flue. Used iso and air throughout. Used bottle brush in the flue from top to bottom (can't get to the whole length, ideas?)

The latest cleaning helped! BUT not enough.  The frig was already cold at 35 degrees from shore power, cleaned the assembly as described, switched the frig to propane for overnight.  Frig temp is now 48. That's better than before when it would raise to 65 degrees overnight. 

NEXT? Any and all ideas are appreciated. Thanks

If the trailer is level, it sounds like there may possibly be a blockage in the tubing. If the tubing on the right is hot, the tubing to the left of it should taper off in temperature and not have an abrupt change in temperature. This might apply:

https://www.trailerlife.com/tech/rv-maintenance-absorption-refrigerators/ - "If the refrigerator is operated off level, then the heating of the boiler is uneven, creating hot spots where the sodium chromate can begin to precipitate out of the solution and form crystals or flakes in the solution. Once formed, the flakes always remain and can create a blockage. Once the blockage forms, the cooling unit becomes damaged and must be replaced at considerable expense."