I checked one of these out a week ago (Dometic RM75), and the cooling unit has a blockage. The freezer got down to -5, and the fridge was 75. You'll need to either replace the cooling unit or replace the fridge.
Oh, and to help you make up your mind about which to do, I installed several cooling units on our own Dometic fridge to no avail, and ended up getting a new fridge from Airstream.
Meddle not in the affairs of dragons, for you are crunchy, and taste good with ketchup.