Freezer fan runs continuously

Freezer and fridge both set on "4" "middle". Freezer maintains consistent 10 degrees and fridge maintains a steady 40 degrees. Fan in the freezer runs 24/7. Repair guy came and replaced the control board but it didn’t fix the problem. Condenser coils are as clean as I can get them. I loaded up the freezer as instructed by the repairman without obstructing anything to put a proper load on it. Fridge section about half full with drinks. This unit gets very low usage so opening the doors too much is not a problem. Any ideas what would keep the freezer fan running forever? It’s been about two months now and it’s still running.