Freezer gets too warm at times on adaptive defrost

I have a brand new GE GTS model, Garage ready, 21.9 cu ft refrigerator freezer-Freezer on top.
The unit works fine for a few days and then, every 3rd or 4th day, the freezer will go from -6 F
to +50 degrees F. This is during the adaptive defrost cycle. The refrigerator section stays within
normal range. GE has replaced the Heater Defrost unit in the freezer, and the main board twice.

But the problem still exists. Tonight the freezer went from -6 degrees F to 55 degrees F.
Any thoughts as to the problem??