I have a Danby 7.5 CU FT refrigerator with a seperate freezer on top. It is propane powered. The freezer frosts up in a day after turning it on. The seal seems tight as a piece of paper passed through the closed door seems to have some drag, but it must be leaking for all the frost to form so fast. The unit is 3 years old but only sees use in the summer for a couple of weeks. Any thought s on how to solve this problem?