I have the enlite with the 640g. The communication between the 2 is that unreliable I have disabled the smartguard function. In a normal week when I check my BGL on the pump it will be having a hissy fit at least 20% of the time. The worst is you cant switch off the alarm (mine is vibrate) so 3:30am it wakes you to tell you it's had melt down... Thanks Medtronic. Apparently the new enlite sensors / 670g are better. To be honest they couldn't be worse. Before anyone asks I had my 5month old pump replaced (with a refurbished pump) and the transmitter replaced. I still find the reliability much better than the Libre.
It rarely records it's problems, well that us mortals can see and it recorded 3 failures yesterday. Don't bother calling Medtronic, they go through the diagnostic's, much like the IT Crowed - "have you switched it off and back on again".
Reasons given
You must be in a very electrical noisy place... On occasions riding a pushbike (no mobile phone because the reception is so poor)
The pump is to far away... what 5cm's is to far away.
You didn't put the sensor in correctly... I do it the way I was shown by the diabetic pump nurse - they even sent someone out to check.
The list goes on