Odors in your freezer can be caused by how food is stored. Some foods have a strong odor, so be sure to cover them tightly. Sometimes odors can also be caused by certain containers and wrapping materials (such as paper, foil, or plastic). If you think this might be the case, try using different containers or a different brand of wrapping material.
After you’ve checked how your food is stored, try cleaning the interior of your freezer with a sponge, warm water, and baking soda.