@dave - We get the ??? under two situations:
- The sensor is at the end of its life and starting to give bad numbers. For us, the sensor quite regularly lasts 12~13 days. So if we get the ??? on day 12, we don’t bother (at this point having done this for some time now) to troubleshoot but rather we just shutdown the sensor, peel it off and get a fresh sensor in place.
- After a shower on Day #1 ~ Day #11. In such a situation, we carefully pop the transmitter out (being careful not to dislodge the sensor). We wipe the transmitter down with an alcohol wipe (the surface that contacts the sensor), let it air dry and then put the transmitter back in place.
NOTE: Not ALL showers. Occasionally. I don’t remember this happening within the last month. But certainly it happens from time to time.
EDIT: In terms of missed readings, we use the app on the SmartPhone so if there are missed readings, they are usually backfilled. So unless we are watching closely at the time, we would not be aware of missed readings looking back in time unless it was a gap larger than 3 hours. The Dexcom Receiver of course does not have the backfill functionality.
I would say it is periodic that we happen to look and see a gap of no current readings but them it would connect and backfill and the gap is gone like it was never there. Hard to say how often but enough that it does not seem an unusual occurrence.