Suburban SW6DE slow ignition

I had an issue with my fridge not lighting at higher altitudes. It worked fine at lower altitudes, but when I got into the mountains it wouldn't lite reliably. I checked voltage, cleaned terminals and pulled out and cleaned the burner/igniter but it still wouldn't re-lite reliably. I finally adjusted the spark gap closer and it works every time now. I'm guessing that the gap needed to be closer because of the lower oxygen level.
Maybe in your case, the propane is building up before lighting off. Try adjusting the gap closer so the spark is stronger.