If your Primex temperature sensor readings are different from those logged by a non-Primex temperature monitoring device. this article provides information that may identify the cause of the reading difference. A secondary temperature monitoring device may be refrigerator's internal sensor or non-Primex thermometer/device.
Determine the reported degrees off.
If reading is 1 or 2 degrees off: two different temperature sensors may never read the exact same. Primex Probes are NIST certified to +/- 0.5 degree Celsius or +/- 1 degree F.
If reading is more than 5 degrees off: do both temperature sensors use a thermobuffer (buffered temperature probe)?
If both are not using a thermobuffer, comparing the two is not accurate. Temperatures measured by a Primex thermobuffer match the temperature of the content more closely, not the air temperature.
Check the placement of the probes. Make sure they are not in two different locations.
Check the probe mounting and verify it meets the Probe/Thermobuffer mounting guidelines.