Both of my Dometic 15000 btu units quit, when my MH was only 3 months old.
Silly me, I was under the belief that having two roof units meant you had some redundancy (if one fails, the other will keep running).
From Phoenix to El Paso, I could NOT find any shop that could even look at it. They were all booked up, and said I had to wait one week before they could get to it! Instead of complaining about the stupid rigging, I got busy modifying the control system myself. I rewired the system such that the two units are completely separate from each other (except for feeding into a long common duct). Yes, I have one thermostat in the living room and one in the bedroom. And, it works GREAT! And, if one goes out it does NOT prevent the other from working! PLUS, it's a whole lot easier for me to diagnose any A/C problem.