Often (2 out of 3) when people try to call me, the phone seems to be offline and jumps directly to my voicemail. A few minutes later I get a missed called text messages to say I missed a call. And that while the phone did not ring once! I did have a network connection
It seems that the phone is on deep sleep or has not connection with the network.
What kind of call did you try to receive? A normal one or a Signal/WhatsApp/other intetnet related call?
And if it’s intetnet-related, did you use mobile data or WiFi? Because your FP disconnects from WiFi when it is in standby for ~10mins, so calls can’t go through.