Several years ago I was having trouble with my fridge keeping cold enough. This was my first RV and I wasn't sure what to do about it so I took it to my local RV dealer. All he did was take his air hose and blow the heck out of the whole area around the heating components. It worked great after that.
Now I carry one of those cans of air (computer duster) and occasionally give the fridge a few bursts of air. Haven't had a problem since. It blows off the stuff that gets into the area where the flame is. I also helped a camping buddy when his fridge wasn't keeping cold enough too. He now carries a can of air.