I just had my first problems with a sensor and thought I would share what happened.
I decided to try a new spot for the sensor and decided on my inner thigh, a couple of inches above the knee. It seems that this spot does not have nearly as much fat under the skin as my belly. :-)
I noticed a little bit more of a sting when I inserted the sensor, but I didn't think anything about it (more on that later). After my two hours, I put in my two calibrations and away we went. Shortly after calibration, it seemed my numbers were climbing pretty rapidly. I did a finger stick and my Dexcom was about 80 points higher. When I input the calibration, it brought the number down and I didn't do anything. Well, over the next 24 hours my numbers were all over the place. They would start rising for no reason, they started falling to the point where I even got the double arrows down alarm which I haven't seen since I started two months ago. I think I've only seen the single arrow down a few times. Every finger stick I did was fine and at least 60 points off from the Dexcom. I also lost connectivity with the sensor multiple times even though I was wearing the receiver on my hip, not more than 18 inches away. The last straw was getting the three question marks and not being able to get it to accept a BG input.
My theory is that when I inserted the sensor I did not pinch the skin from the sides and got the sensor through the skin and into the muscle. There was some tenderness around the site, which I have never experienced around the sensor. I guess I didn't have to worry about this issue when I was putting the sensor on my stomach.
I have since inserted a sensor in pretty much the same spot and have been getting great numbers just like always. I guess I'll just have to be more conscious of the skin pinch when inserting the sensor in a spot with less body fat. I'm hoping that will become more of an issue in the future.