Ours went offline at 11:07 - I just woke it and it immediately went back online.
I saw something similar within last week or so, but didn't explore, thinking that it had just slipped out of range of wifi - which I now understand is not maintained when car is asleep so probably not that. So not really sure what is going on with it starting to go offline and TeslaFi not recording it as such every minute or so - header showed it correctly as offline though. I probably need to check my TeslaFi settings to see if anything changed there.