The only time I've seen loss of signal on my mobile using a G5 transmitter, is through using xDrip but this usually rectifies itself over 1 or 2 days using a new sensor. Once a few days have gone past, the sensor and transmitter behave and the loss of signal only happens if my phone is downstairs and I go upstairs or I go outside.
Using my upper arm I usually get about 20 days of reasonable data but after that, I get noisy readings with 2 arrows going up followed by 2 arrows going down and then horizontal arrows followed by random dots everywhere. I then do a blood test to see what my true bg levels are and do a calibration. This works for a while but the same thing happens the following day and it starts to get worse. I now try to get my money's worth out of these sensors so when it looks as though the G5 is failing, I swop over to using the same sensor with a G4. So far, the same sensor has been in my upper arm for 39 days. Not sure how much longer it will go on for but if it goes to 40 to 45 days, then that will suit me.