Missing data points in time series chart - Community

Two devices, two databuckets and one dashboard are present in my ThingerIO account.
Only one device is sending data. It transmits over LoRaWAN to The Things Network and from there data are correctly saved into a ThingerIO databucket.

Please see the linked data exported from the databucket (some columns were redacted for publishing):
https://docs.google.com/spreadsheets/d/1NUI5c4zORKKd2dyk9vr0lbVI4Xble1f9GfNZEzxvZH0/

Here are my stats:

Thanks in advance for any hint around this topic.