I called Dexcom on Friday to report the tape not working on the lot that was sent to me. They were willing to send me two more units to replace the two that detached from my body. I just asked the guy to put it in my file and to tell the tech people that there seems to be a problem with this lot.
FWIW I have also had problems with the adhesive on several sensors. I gave up waiting to talk with someone when I called Dexcom, so I covered my sensor with "Hypafix" tape. I am allergic to Tegaderm and the IV3000, but so far the Hypafix works well.