As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE, STARTED TO FEEL A LIGHT FLUTTER IN THE HORIZONTAL AXIS (NOSE UP AND DOWN). SLOWED AIRCRAFT TO .77 AND TURNED OFF TURBULENCE MODE AND FLUTTER STOPPED. REPLACED ELEVATOR SERVO ACTUATOR. REMOVED AND NR 2 AND NR 3 ELEVATOR PCU'S AND REPLACED NR 1 PCU ROD END BOLT AND BUSHING IAW AMM 27-33-01.P/N: 27600-3, S/N OFF: MAL-0664, P/N: 27600-3 S/N OFF: MAL0420, OPERATIONAL CHECK GOOD.