Apple Fixes Reboot Bug in Watch Series 12 and Ultra 4

Apple Inc. launched the Apple Watch Series 12 and Ultra 4 featuring a new Readiness tool that assigns users a health score from 1 to 10. The feature uses heart rate variability, sleep, and fitness data to suggest daily activity levels across four tiers: Recover, Pace Yourself, Ready, and Go For It. Users must log seven nights of sleep to activate the tool.

Immediately following the launch, early adopters reported a critical bug where devices restarted without warning during activities such as using Maps, Siri AI, or while idle. Diagnostic logs indicated the crashes were caused by a Neural Engine timeout, where a firmware watchdog forced a restart after the hardware stalled.

On Wednesday, Apple released watchOS 27.0.1 exclusively for the Series 12 and Ultra 4 models to resolve the instability. The company stated the update provides bug fixes for an issue where the Apple Watch may restart unexpectedly.