I bought a Forerunner 945 LTE from garmin.com and received it on Jan 11. I took it out for a walk that day and it worked seamlessly.
At some point between Jan 11 evening and Jan 12 mid day, the watch installed at least one software update. I had seen the message like “sending update to watch” in the app, but I did not start the update, so I can only assume it started by itself.
Since then, my activities crash, often at the 1:04-1:05 mark, with the watch restarting.
See this series of activities. I was swimming in open water between two poles roughly 100m apart.
I read somewhere that it might be a wiring issue, so I started a walk session on the couch. Same result. In particular, same 1:04 duration before the crash.
Between the timeline of the update and the fact that the crash happens at the same duration, I’d say this is a software, not hardware issue. Fingers crossed, I guess. Otherwise, the watch is unusable as a training device, and I'd have to send it back.
I’m based in Australia and experienced the issue on LTE. I saw another post of someone saying they were in Australia when the watch started playing up.
For what is worth, I hereby give Garmin support staff approval to access my data in order to diagnose this issue.