Yup, high humididty will do that.. These are NOT frost free units, you have to defrost them from time to time.
If there is no food in it Simply turn it off and prop the doors open..
Make sure the DRIP TUBE on teh outside extends out one of the vent holes so it drips on the ground not the power connections board.
Put a towel in the freezer (on the bottom) to absorb melt (bath towel, clean)
Then when dry wash with baking-soda water and restart.
IF there is food in it.. Transfer to one or two chest "Coolers" (picnic coolers) or transfer to sticks and bricks fridge till defrosted.
I have a second freezer in my RV so I just eat it down a bit and then defrost, Likely around the 22nd of the month (pay day is just after that).
One thing you need to check is your door seals.. If the door is not sealed it ices up faster.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times