I determined that it was a problem that occurred during the defrost cycle by resetting the GFCI outlet and forwarding the defrost timer until the defroster came on. Once the defrosting began, the GFCI outlet would reliably trip. I took apart the shielding inside of the freezer and tested the defrosting without the heating element or the thermostat connected. Since that looked good, I tested for proper functionality of the thermostat by removing it, placing it in a working freezer, and checking for continuity when cold and no continuity when at room temperature. Since that looked good, I assumed the problem was with the heating element. Upon replacing the heating element, it ran well. Replacing the handle and installing the feet took little effort.