That's exactly what I was thinking. My son's has vibrated itself off the nightstand more than once . . .
I called Dexcom today, and started a new discussion about what I learned: see
Broken G4 "rail" (that keeps the USB sliding cover in place)
This totally explains how one of my cat's hairs got into the 7+. That was bugging me for months. I thought it was a crack until I noticed the tipping on the hair.