Hot tub thermometer data gaps - IBS-M2 and IBS-P02R

I have been using the IBS-M2 and IBS-P02R for a week now. It is used to monitor the water temperature in my hot tub while I am not at my cottage where the hot tub is located. We are prone to power outages and I don’t want the tub to freeze as it gets very cold here.

I have it set for 5 minute readings. Today I noticed that it didn’t record any readings for an hour, so I thought it might be dead, but then it started recording again. I also looked at the data and since the beginning it hasn’t always recorded data every 5 minutes, sometimes it is 10 or 15 minutes intervals. The battery is good.

Does anyone have this issue or know why it stopped recording for an hour today. The IBS-M2 data was still recording during that 1 hour that the P02R was not, but I also noticed that there are some 10 minute data gaps randomly as well on the M2. Thanks.