Are the doors left open for long periods of time?
Frost is likely to build up if the door is left open for a period of time, allowing humidity to enter the freezer. Make sure the door is closing completely and is not blocked by something between the door gasket and cabinet.
Are the doors opened frequently?
Frequent door openings can let in humid room air. Keeping door openings to a minimum will help, but may not completely eliminate frost or ice in the freezer. During months of high humidity (especially if a home is not air-conditioned), it is normal to see some frost and sweating on the interior walls or on food packages.
Are the doors sealing correctly?
An improper seal of the gaskets on the refrigerator or freezer doors could also cause humidity to form. Check the seal around the outside doors and the freezer door to make sure nothing is obstructing the gasket seal.
Are the air vents blocked?
Blocked vents can cause a couple of different issues including moisture build-up or excessive frost. In order to help the moisture build-up you need to allow room for proper air flow between the freezer and refrigerator compartments. Cool air enters and exits the refrigerator compartment from the freezer compartment through vents. Depending on your model, these vents are in different locations.
CLICK HERE for more information on ensuring proper air circulation.