If it's a residential check the heat exchanger coils and fan for dust bunnies.
If it's an absorption refer try moving the thermistor UP on whichever fin it's mounted on. If that doesn't work try searching this site for 'the Muddypaws mod'.
My Norcold, (yes, the much maligned Never-cold) with that mod stays right at 34F and the freezers stay at -18F.
I've seen several installs done by a large Manufacturer (who's name starts with a W) with about 6 inches of gap between the coils and the wall. Messes up the airflow and makes the poor thing barely work. Make sure it was installed correctly as per the manufacturers specs.
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