As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FLIGHT, PILOT FELT A VIBRATION IN THE AC FOLLOWED BY ATTITUDE EXCURSIONS IN THE PITCH AXIS. THIS OCCURRED OVER A PERIOD OF APPROXIMATELY (2) MINUTES AND FELT SIMILAR TO GOING OVER A SERIES OF SPEED BUMPS. THE PILOT ELECTED TO MAKE A PRECAUTIONARY LANDING AND NOTIFIED MAINTENANCE. TROUBLESHOOTING INDICATES THE VERTICAL GYRO AT FAULT.