https://www.cnet.com/news/apple-watch-os-5-1-update-causing-problems-for-some-users/

We've reached out to Apple for comment and will update this story when the company replies. But in the meantime, you should skip this software update for now.

The big improvement of Watch OS 5.1, which is available for download alongside iOS 12.1, is that it will now automatically call emergency services and play a recorded message, saying that a fall has happened and offering location information (latitude and longitude). The watch already could make emergency calls after falling, but didn't send an audio message (instead, an emergency message with location information was sent to a key emergency contact).