This bottom freezer unit #79578092901 is building up heavy frost in the freezer outside of the access panel. It is defrosting properly, it acts like it has a bad seal and is letting warm air inside the freezer but there are no air gaps any where, and the door shuts properly.
After checking for gaps, I thought the unit was staying on for too long, also the customer stated he thought some items felt really hard like it was staying well under 0, so I replaced the control board and freezer thermistor. Customer called back about 5 days later and said it still is frosting up.
I can't really think of anything else that could cause this.