As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) THE PILOT NOTICED N1 INDICATION REDUCED FROM 91 PERCENT TO 81 PERCENT WITHOUT COMMANDED THROTTLE INPUT. THE ACFT HAD A CHANGE IN YAW SO THERE WAS THRUST REDUCTION. THE N1 ROLL BACK LASTED 5 MINUTES THEN CAME BACK TO 91 PERCENT N1. TROUBLESHOOTING IS ONGOING.