Confirm the reading
Verify the controller against an independent thermometer before assuming a refrigeration fault. Probe failure is common.
Inspect the door
A door left ajar or a failed seal introduces warm humid air, which shows as ice on the floor and walls and a room that never recovers.
Check for ice on the evaporator
Heavy ice indicates a defrost failure. Continuing to run the room in this state risks compressor damage.
Listen to the plant
A compressor short cycling or a condenser fan that is not running are both immediately visible signs, and both need attention before stock is affected.