I've been using Dexcom since December last year and it's generally been very reliable and accurate.
However, my latest couple of sensors have had the "???" error occuring fairly regularly, especially when renewing the sensor for a second week. I have not taken any paracetamol.
Is this normal and are there any tips to help avoid this error?
I have only used the dexcom a few times but, like you, I experience ??? in th e second week.
I was told this is likely due to my body being "distressed" around the sensor. Actually, this is possible: although I used ski racer, I was itching around the sensor.
Someone on this forum suggested I tried using the sensor on my upper arm. I have not tried this yet.