External Power Sensor stops working

[Jimbo Automates]

I have a very new External Power Sensor in a freezer that works for a few days then stops.  I pull it out of the freezer and it still doesn't respond disconnect the battery and reconnect then it starts working again.  I left it out of the freezer for a week and it worked fine, then stopped sending updates after less than a day which you can see in the attached chart.  The Moisture/RH doesn't seem that bad so what is causing it to stop sending updates?