The release of watchOS 5.1 update was bricking some Apple Watches. Apple quickly pulled the release “as a precaution.” Now it seems like the problem has been fixed. On Monday, Apple released Watch OS 5.1.1.
Note that if you installed watchOS 5.1 and it caused your Watch to lock up, you should still contact Apple Support — 5.1.1 won’t fix the issue by itself.
Watch OS 5.1.1 also includes fixes for Walkie-Talkie and Activity award issues.
The watchOS 5.1 update added audio-only Group FaceTime, 70 new emoji, more watch faces and improved fall detection on Series 4 devices.