As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEVELING AT FL39 M.8-AIRCRAFT EXPERIENCED AN UNUSUAL VIBRATION IN YAW/SHAKING, WITH A SLAPPING NOISE TO THE RIGHT OF THE COCKPIT. ALL NORMAL WHEN THRUST RETARDED FROM CLIMB THRUST, SOUNDED AND LEFT LIKE A DOOR OR PANEL WAS OPEN. REMOVED AND REPLACED THE NR 2 ENGINE IAW BOEING MM.