My Garmin HRM dual failed. Was reading really high 230 bpm +! Took it off 36 mins into workout and the backing plate just fell off with all 4 screws still in place! It can't be repaired because the holes of the backing plate are now larger than the screw heads. Corrosion was also discovered on the battery. Unit binned. Why does it need to have a more complex design than their other sensors which only require a flat head screw driver or a small coin to access the battery compartment? After the older Garmin HRM just stopped working about 2 years ago and this one falling apart I've lost patience and replaced it with a Polar H10. Has anyone else had this experience?