We had resounding success with our first two sensors, almost perfect accuracy, very good range. Like you, I don't like that it doesn't alarm if it goes out of range or for ??? Our third sensor had the same ??? issue as you, and likewise, when I called, they said they would replace it. We had ??? for several hours, then some readings and then ??? again. Switched it out and are having great accuracy again. I loved having the Mysentry and the readings on the pump, but we had such horrendous accuracy that now seeing how a CGM can work, I am so glad we made the switch- really what is a CGM's worth without accuracy?