We had similar problems with our Dometic refer. We checked the installation manual and found several items not done to the install.
First, the space above the fridge box should not be there. Second,
a curved piece of sheet metal above the condenser should be installed to
direct the hot air out. Third, the space between the outside wall and
the coils should be about 1". If not, a baffle should be installed above the lower louvers. We did these improvements, and now get 35-38 degrees
inside the fridge on 85 plus degree days.
Hope this helps.
http://americanrvcompany.com/assets/images/AmericanaInstallationOperation.pdf
Pages 4 and 5 show this.
Ed