I'm on latest version 13.35, I don't know how it would be on earlier, because my MTB season just starting.
I went for a training to prepare for MTB race on weekend, I have loaded GPX with the trace, started MTB activity and selected loaded trace. After around 1 minute of riding, watch restarted. It rebooted and asked me again if I want to continue, so I resumed and followed the trace. after around next 10 minutes, it rebooted again, and then again. During 24 km ride it restarted around 7-8 times, I stopped counting. I've decided to restart activity, but after restarting it was the same. Even I tried at home the same process, it was also rebooting after capturing GPS fix.
That was so disappointing experience. I'm coming from generation of F5, F6, F7 and this one is the most buggy expensive watch I've ever had. Garmin - Wake Up. You are making America small again.