As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED THAT WHILE AT CRUISE FLIGHT 380, WITH ENGINE SYNCRONIZATION ON, BOTH ENGINES ROLLED BACK FROM N1 AT 98.0 TO 90.9, OAT WAS -63 DEGREES. THE ENGINE SYNCHRONIZATION WAS TURNED OFF AND ENGINE IGNITERS WERE TURNED ON. THE CREW WAS THEN ABLE TO INCREASE POWER. A LARGE THROTTLE LEVER SPLIT WAS OBSERVED AND THE LEFT ENGINE GAUGES WERE FLUCTUATING. AIRCRAFT LANDED WITHOUT FURTHER INCIDENT.