So is it NOT working fine when you take it to dealers, they "fix" and it then again breaks? Your comment about the rear being hot makes me wonder if the fans really are working, or the fridge is installed with the proper baffles ? It might be warm, but if the cavity is hot, that's a problem.
FWIW- even though I converted to Helium, we went from 68 degree day temps, to 108 for 3 days, and the fridge never left 33 degrees and -2-+2 in the freezer on setting of 5. That in large part is due to the improved rear airflow