As for the syncing and re connection problem you are experiencing, we are researching this to determine the cause. I apologize for any inconvenience this may have caused.
I rolled my Garmin back to v10.0
Now working fine!
This is taken from a post on Singletrack forum.
Old firmware versions available here: http://gawisp.com/perry/edge/
Download the version you want, then rename the file to GUPDATE.GCD, and copy it to the Garmin folder on the Edge. Then unplug it and switch it on, and it should install that firmware version.
Tested over the weekend. The roll back to v10 didn't solve the issue. I am now convinced it's the app that is the problem.
After clearing cache and reinstalling GC the pairing works. I can turn off the Edge 820 and the bluetooth and they will auto re-pair when turned back on. However, restart the phone or stop and restart the app and the bluetooth pairing is screwed. Only way to get connection back is to unpair, clear cache and re-pair the devices. What a faff.
Hopefully Garmin will get this sorted soon.