I am on my third sensor and it seems that early in the sensor life I tend to get a lot of ??? during the evening and night. For example, I started my current sensor on Monday and the past 3 nights (including right now), I get ??? starting around 7pm and that will last throughout the night until about 30 minutes after I shower. I have had this last from 10 hours up to 16 hours. I finally found a spare moment to contact Dexcom this evening and basically was told they really aren't sure why this is occurring. The reasons could range from my insertion technique, to where it is placed on my body, to even in the very rare case of the sensor not working well with my body's chemistry. I was basically told to insert a new sensor and they will send me a replacement. Has anyone had issues like this? Any tips or ideas? I am at a bit of a loss because I *thought* I was doing everything correctly.