Frost/Ice build up Dometic Refrigerator

This is going to sound strange, but this is what happened to me. (If you do not use ice trays to make ice cubes in your freezer, skip the rest of this message.) We had ice build up after only about 2-3 days. I would defrost it and 3 days later have to defrost it again. I checked everything mentioned here including putting in a fan. No results. My wife loves her Manhattans in the evening so we continually make ice cubes in ice trays. On one trip she went off her Manhattans, so I did not make any ice. Guess what? No ice build up in the freezer. For the last couple of years I have either made ice by putting the trays in a large plastic zip lock bag or I have gone to a convenience store with a large zip lock bag and ask them if I could buy some ice from their soda machine. Never has anyone asked for money. I don't have room in my freezer to buy a "bag" of ice.