Only use an instrument designed for the temperature range and conditions involved. A room thermometer may not measure sufficiently low temperatures or tolerate condensation appropriately.
What the observation tells you
A display showing its minimum value can be mistaken for a genuine reading. Battery performance, sensor placement and response time also matter. Repeatedly opening the cabinet to watch an unsuitable instrument will not produce dependable evidence.
A useful next step
Choose a freezer-suitable thermometer and follow its instructions. Record where it is placed and any recent loading. If the reading conflicts with obvious thawing, do not dismiss the food concern while the instrument is checked.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.