Opening the door admits warmer room air, so a changing air-temperature reading during a long inspection is not a clean test of normal storage. Keep checks brief and compare measurements under similar conditions.
What the observation tells you
Cold food changes temperature more slowly than the air around it. This means a brief air fluctuation cannot describe every item's history, and a cold-looking display cannot establish that food was always safe. Leaving the door open to watch the thermometer also creates the condition you are trying to measure. Repeated rearranging makes that problem worse.
A useful next step
Write down a settled reading, the measurement position and any recent loading or prolonged opening. Close the door between checks. If the appliance cannot return to suitable storage conditions, protect perishable food and arrange assessment; do not dismiss a persistent problem solely because some change after opening is expected.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.