Some new Apple Watch Ultra 4 and Apple Watch Series 12 owners are reporting unexpected reboots, with diagnostic logs pointing to the Apple Neural Engine as the cause. Reports surfaced in the MacRumors forums following Friday's launch, with around 30 users describing sudden restarts during activities like using Siri AI, editing watch faces, opening Maps or the App Store, starting calls, and recording workouts. Some reboots occurred while the devices were idle.

At least four owners shared "panic-full" diagnostic logs showing an identical Neural Engine timeout. In each case, the Apple Neural Engine hangs for roughly two seconds before a firmware watchdog triggers a kernel panic and forces a restart. The issue persists on both the original watchOS 27.0 build and the day-one update installed during setup. Erasing the watch and setting it up as new has not resolved the problem for some, and one Series 12 owner reported a replacement unit exhibited the same Neural Engine panic.

Similar complaints have appeared on Reddit and Apple Community Support, indicating a widespread problem. Apple has not yet acknowledged the issue.