Alternative theory: I believe this is a symptom of a blocked freezer drain. When the automatic defroster runs (which I suspect is working fine), it heats up any ice buildup on the evaporator, turning it into water. However, that water now has to go somewhere, otherwise you've just relocated the problem -- once the heater turns off again, the water will simply re-freeze wherever it now is in the freezer unit.

To avoid this, there is a drain hole below the evaporator which will allow the defrosted water to exit the freezer compartment and collect in the drain pan underneath the unit, where it will evaporate naturally.

If the drain hole is blocked, the water will instead remain inside the freezer, eventually filling up the bottom of the evaporator compartment (which is usually behind a cover at the top rear of the freezer) and running down the rear wall of the freezer to collect at the bottom, where it will slowly form a mass of ice.

Some links that might be useful:

https://www.applianceblog.com/mainforums/threads/ge-profile-ice-at-bottom-of-freezer-section.17777/
https://careandrepairs.ca/how-to-fix/refrigerator-repair/defrost-drain-is-clogged/