I have the same problem… if I toggle the iPhone contact access it worked for a while ( hours) then some thing happened.tried the soft reboot and the hard reboot and power cycle the I phone still same issue.
Follow up: the service center diagnosed the second battery marginal and replaced both of them! In and out 1.15 hrs. Kudos to the Dallas service center!
Here is what you get: I am at a second visit to the service center to figure out what is going on. On the first visit they recalibrated the sensor then24 hrs later it appears again. I can still drive it but it is concerning that I can’t see if it is charging, charged or it will die …