Also, verify that your condensate drain (back of refrigerator) has a RESTRICTOR in it. If just an open-ended hose, it will let a lot of humid air in.
And, a suggestion on defrosting:
Turn refrigerator off at least one hour before defrosting.
Remove all food from freezer-- into an ice chest if you have one. Plastic tub second choice, sink third choice.
Leave both doors open and use a hair dryer on LOW to defrost. Do NOT get the hot end of the hair dryer inside the frame of the refrigerator. This will materially speed defrosting, but hot pose a danger to the plastic of the refrigerator itself.
Whole think should not take 15 minutes. If it takes longer, you need to defrost more frequently.