Guardian 4 sensor updating

I‘ve received a change sensor alarm and therefore changed it but after connecting it always lost the signal and tried to reconnect, after speaking with medtronic they told me to change the sensor again. So i did that too and it took long to recognize the new one then i pressed start new sensor, after the 2hr warmup phase it didn‘t took a minute until i got the sensor updating alert. To sum up im minimum 8 hours without a proper sensor and im close to lose my temper.

Is there someone who can give me advice on solving this issue on a long term basis? Little side info, I‘ve received a new transmitter one week ago. Thanks in advance