Crash / Reboot during activities

Maybe it's that well-known bug that I have too. A soft reset will help and the restarts will disappear for 5-7 days. Hold the ctrl button until the watch turns off, then turn it on. Write if it helped.

Are you using navigation during the workouts and/or the runs are long (2h+)? 

ok.. i try.. after i wrote this thread, i reset my garmin.

nope.. i dont use navigation, and only runs 1 hours 30 mins only

I had that in that version as well , I updated to 9.27 since than I only had once where the watch kept buzzing , no crashes since the update 

I'd recommend wiping all history (option in the watch). Takes seconds and so far has prevented the issue for me for 1-2 months now, including my 5.5h (8h total with breaks) 130km bike ride.

Disable Physio True UP as well or whatever it was called, as it re-syncs your past history, therefore filling the memory again.

I delete the history regularly every week...

I do it daily or every other day. My watch would crash after 4-5 days if I didn't, so I don't want to risk multiple days without clearing. >_<;

Then I'm missing statistics like the weekly sum of how much I run. I think the watch should handle this. But the watch crashed even after deleting the activities many times, so it has no effect.