We experienced the same problem with a Dometic Refrigerator. We would find the "Check" light on at random intervals, particularly at 8000 ft plus. We'd also get the problem parked at home (6200 ft). Got the same story from the dealer when we took it in.
I ended up ordering a new spark element, but never installed it as I first tried cleaning the electrode with emery cloth and then reset the spark gap to the value in the manual. Problem seemed to go away for a trip to Tetons and Glacier. We traded the trailer shortly afterwards for a Class A that has a Dometic refrigerator. We were in RMNP at 8500 ft a couple of weeks ago and had no problems.
I think you can get a kit with a high altitude orifice, but then you may have a problem at low altitudes. I never got that far though.
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