This happened to me yesterday as well during a very short hike with my Race (running the latest firmware). The total distance was just under 10 km, and after about 2 km, my Race froze and then automatically restarted after approximately 60 seconds. If I hadn’t happened to look at the display at that moment, I wouldn’t have even noticed it. However, since I did, I was able to restart the activity after the reboot. In the end, the first 2 km were still saved, but at the end of the total distance, I had two separate recordings, and a few hundred meters were missing.
The real issue, though, is that I can no longer trust my Race. I never had such a crash with my S9B-Ti, and I will probably switch back to it and sell the Race. A watch that fails in such basic functions is useless to me. It doesn’t matter how much I like the Race otherwise.