A little story. I had a Norcold that came with a previous boat. I always hated it because of its small capacity. I bought a new Tundra, which I don't believe is made anymore, and when I took out the Norcold and after it had been sitting outside I found about 2 inches of ice below the freezer compartment. No wonder it was running all the time! This ice was not noticeable while in use. Maybe this is your problem.
The five stages of life: Sailboats, Motorboats, Motor Homes, Nursing Home, Funeral Home.