I have an MFI APP 6302 Larder type fridge, and my problem is that the motor/compressor seems to be running all the time and there is a always frost at the back, even though I have it set to level 1.
An engineer came recently and replaced the thermostat but it hasn’t made any difference.
I would suggest at this point and with the information you have given that either your fridge is short of refrigerant or else there is a problem with the motor (compressor) If you go to the section ‘repairs @’ you will find someone to help you out. Its not a job for the unexperienced.