As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT LEVELED AT 370 AND POWER RETARDED, AIRCRAFT DEVELOPED A SMALL VIBRATION. VIBRATION FELT IN FLOOR AND YOKE AND WOULD CHANGE WITH POWER CHANGES. ALL PARAMETERS NORMAL. WHEN LEFT ENGINE WAS SHUT DOWN AT GATE AND DECELERATED VIBRATION GOT WORSE AND AIRCRAFT ACTUALLY WOBBLED AS ENGINE SPUN DOWN.