I'm also experiencing this frequently. The Garmin device silently and randomly resets itself to the home screen and discards all collected data. No trace of it can be found when synchronizing with the app. It's as if the activity was never started.
HI there! I am sorry to see you are experiencing this. Can you sync the device with Garmin Express then unplug and reset the device to defaults. Then can you tell me if the device reboots again after that?
Thanks for responding. I've factory-reset the device many times. It has also received a firmware upgrade. Nothing has made any difference. The error is persistent.
Are you located in the US or CAD?
Ok! Here is the support for Garmin Europe Please reach out to them so they can get this resolved!
I am now also experiencing this problem semi-regularly, it started roughly 3 weeks ago on my vivosmart 4 (SW 5.10, TSC 2.20 SNS 6.0) . I start an activity and about 20-60 mins in the watch buzzes, displays a triangle, and then goes back to the home-screen, with no trace the activity ever started. When synced with connect, the portion of the day is just missing for steps/HR/bodybattery etc as if the watch was off during that time.