Our Dometic fridge would get a bit finicky when we were at Morraine Park in Rocky Mountain NP. (8000 ft) During the day it would usually light and burner would cycle on/off as needed. At night it would usually go into fault with the check light coming on after three attempts to light. I know you were able to purchase a high altitude “nozzle” that was supposed to help but I never bothered since most of our camping was at much lower elevations. Didn’t have a problem with water heater or furnace. We haven’t had our new unit that high in elevation yet but wouldn’t be surprised if the results were the same.