There are many factors that can effect your search for refrigerator
cabinet insulation properties or the lack of!!
Suggest having a heat load calculation done for that specific cabinet so you know what it should be if the insulation is ok.
To obtain this you would need to know and advise the interior
dimensions, insulation thickness (and type if possible). Also inner lining material, and the average environment
temperature. This would provide you with an hourly cabinet heat load in Watts/hr if the insulation is ok.
Then test as follows to ascertain your actual insulation quality for comparison
Using blocks ice to absorb cabinet heat, allow to settle at storage
temp, say 2degree C and note/ weigh how much ice is left by Kg.
Establish ice cooling
expectation by multiplying the Kg of ice left by 90. Each Kg of ice should now be able to absorb approx 90 Watts of heat before complete thaw and cabinet temperature rises. Keep cabinet closed and time, monitor
cabinet with remote
digital thermometer and note how many hours before ice fails to maintain cabinet temperature and temp rises.
Divide total watts of hold-over ice by the hours cabinet temp was maintained and you will know the actual heat load watts / hour of you cabinet and now able to compare with what it should be. Suggest within 80% would be acceptable.
Hope this helps and is not too complicated, besides re-insulating is a sod of a job especially if found later to be unnecessary!!!