LG Error code "E-FF"

Brand: LG
Model Number: LRFXC2416S
Main Symptom: Error code
What happens & when: Error code “E-FF” will display for 2-8 hours, then go away. Then display again about 3-8 days later. This keeps repeating.

Error Code (if any):E-FF
Parts or tests already tried: The unit has been unplugged twice for a complete thaw. After a week or two the code displays again. Then repeats once a week, only to go away again.
Photos / video link:

It sounds like the freezer is not defrosting properly, which would cause ice to build up on the fan and cause this issue. With the power supply cord unplugged, the defrost heater and the defrost control assembly can be accessed in the back of the freezer. This will allow them to be tested directly. The defrost control assembly is made up of an aluminum wrapped fuse that should have continuity, and a sensor that should measure resistance based on temperature (see attached image for resistance to temperature chart). The defrost heater can also be tested for resistance and it should measure between 62-70 Ohms. There should be a product code or a /## number near the model that would be needed for part number accuracy. What test readings do you find and what product code or /## does your appliance have?