Here's Apple's official statement on the issue:
Due to a small number of Apple Watch customers experiencing an issue while installing watchOS 5.1 today, we've pulled back the software update as a precaution. Any customers impacted should contact AppleCare, but no action is required. We are working on a fix for an upcoming software update.
News of the problems with the software update was reported by 9to5mac.
The Big Improvement in Watch OS 5.1 What an enhancement to its case detection system 5.1 what successfully installed, a detected case would be followed by a recorded message to emergency services, offering location information (latitude and longitude).
The added audio message is The Apple Watch Series 4 has already been credited with helping […]
Apple has recently released an update to the Apple Watch Series 4 that adds electrocardiogram (ECG, so-called ECG) functionality before the end d of the year, but the company has not specified a date.
First published Oct. 31, 2:50 p.m. PT
Update, 7:30 pm : Apple Watch Series 4 review : Bigger, faster, more health-conscious – but not quite perfect