As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: UN-COMMANDED PITCH OSCILLATIONS OF UP TO +400 -200 VV1 AT CRUISE ALT FL210 , AUTOPILOT 1 +2. MAINTENANCE REPLACED ELEVATOR SERVO CONTROL 34CE1 AND ACCOMPLISHED A SATISFACTORY LEAK / OPERATIONAL CHECK PER AMM 27-34-51.