Since today, out of nothing (I was just working in my office, no activities being recorded), my Instinct 2 Solar Tactical was frozen (display not being updated anymore, stuck on watch face) so I did a hard-power-down (keep Ctrl pressed).
On power-on, it booted up ok, started to sync, but then suddenly rebooted.
And this is happening in an endless loop now. It will boot, run ok for a couple of seconds, and then reboot during sync.
So I tried a full factory reset (delete all settings including activity data) and also deleted storage/cache of Garmin Connect app on my Android phone before paring the devices again.
It didn't help.
This reboot cycle does not seem to have an end and I suspect it is triggered by something retrieved from Garmin servers, e.g. activity data, because I had deleted local storage+cache of Garmin Connect without any luck.
Instinct firmware seems to be up-to-date: 14.12 (30c71f0)
And there are no watchfaces or apps from ConnectIQ store installed which could be the culprit.
As a workaround, I have disconnected the watch from the phone => no issues since, so I'm 100% sure that it's related to syncing.
How to proceed from here?
