Commercial Freezer Won't Stop Running (Frigidaire Model FCFS201LFB4)

[Clumsy]

So my Commercial Freezer (20 cu ft) started running all the time. It's gets cold (0 degrees F or lower) and won't shut off. The evap fan runs all the time and the compressor runs all the time. The condenser fan runs & the coils are not clogged up. I replaced the thermostat (Cold Control Dial) but it still won't stop running.

The defrost timer does work (periodically the defrost cycle will engage and the evap fan stops running for about 15 minutes) but as soon as the defrost cycle completes the evap fan starts running constantly again. The defrost heater & defrost thermostat do work. I can feel the heat from the defrost heater during the defrost cycle. I don't feel any heat after the defrost cycle completes.

What else could be causing the evap fan & compressor to keep running? The door seal is not leaking and the freezer does get very cold and stays very cold. The thermometer inside the freezer reads 0 degrees or below. The thermometer is a separate mechanical device.

[evaappliance]

Is the light going off when you shut the door ?