Freezer is icing up.

The freezer is on the bottom on this model.

The freezer is icing up. I cleaned out the freezer and also cleaned/vacumed the bottom of the refrigerator. No ice was on the evaporator or anywhere else externally.

When I plugged the unit back in the freezer had moisture dripping inside. Now 24 hours later the freezer is icing up again.

What part or parts could this be?

I see a part called a Bimetal Defrost Part#
AP3108454.