As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 4554 THE CREW REPORTED THAT AT 30,000 FEET IN LIGHT CHOPPY WEATHER HAD AN UNCOMMANDED RIGHT TURN FOLLOWED BY RED "AP" ON PFD AT 2,500 FEET. THE AIRCRAFT YAWED NOSE RIGHT WITH ONLY YAW DAMP ON. THE AIRCRAFT WAS REMOVED FROM SERVICE. REMOVED AND REPLACED THE AUTOFLIGHT GUIDANCE CONTROLLER AS PER AMM#22-11-01. THE OPERATIONAL CHECK WAS GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.