I learned to
- apply new sensors several hours before the previous one stopped
- always use the other arm for the new one
- always wait after swabbing the skin, to allow all the alcohol to evaporate
- during application, after pressing the sensor onto the skin, wait before withdrawing the applicator
- then press firmly directly onto the sensor to be sure it is fully and firmly attached
- as soon as the older sensor stops functioning, rip it off, so that I could not rescan it in error after starting up the other sensor (scanning both sensors really screws up the operation of the reader)
Since then, they operate perfectly. I never link my phone: only use the Abbott reader.