MacRumors: Apple Watch Series 12 / Ultra 4 owners report Neural Engine reboots

MacRumors’ Tim Hardwick reports that some new Apple Watch Series 12 and Apple Watch Ultra 4 owners are seeing unexpected reboots — the Apple logo appears and the watch restarts — with diagnostic logs pointing at a Neural Engine timeout.

Reports have shown up in the MacRumors forums since the models launched on Friday. Owners describe restarts while using Siri AI, editing watch faces, opening Maps or the App Store, starting phone calls, and recording workouts. Some say the watch rebooted while it was apparently idle.

What the panic logs show

At least four owners shared “panic-full” logs with the same Neural Engine timeout pattern: the Apple Neural Engine appears to hang for about two seconds, a firmware watchdog triggers a kernel panic, and the watch restarts.

The behavior has been reported on both the original watchOS 27.0 build and the day-one update downloaded during setup. Some owners still saw reboots after erase and set up as new. One Series 12 owner said a replacement unit also hit the same Neural Engine panic.

How widespread — and what Apple has said

MacRumors counts about 30 owners in its forums thread so far, plus similar reports on Reddit and Apple Community Support, and characterizes the problem as pretty widespread. Apple has not acknowledged the issue.

This is owner-reported evidence summarized by MacRumors — not an Apple confirmation of a bug, recall, or fix. For earlier Series 12 coverage, see our Quantified Scientist heart-rate accuracy piece, Series 12 hands-on on health sensing, and September 18 first-arrivals availability.

Sources: MacRumors — Tim Hardwick (Monday, September 21, 2026, 2:08 a.m. PDT).