Hello,
Tonight the Watch was FW updated to version 15.00,
After update to ver. 15.00 the Fenix 5X was reset few times during MTB activity, and also was reset during scroll widget.
After the watch reboot it returned to the MTB activity collection but it was paused, I had to press on the start button.
It looks like it didn't lose the GPS information, after boot it connected a straight line btw the last point before the failure and the first point after boot. but in HR data I could see only the last segment of the training (probably after the last reboot.
