As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WE HAVE BEEN EXPERIENCING A VIBRATION DURING DESCENT. AFTER SUBSTANTIAL INSPECTIONS, TESTING AND CONSULTATION WITH ATR, A CHECK WAS CARRIED OUT TO MEASURE THE SPRING TAB FOR WARPAGE. THE RESULTS WERE SENT TO ATR FOR ANALYSIS. THE WARPAGE LIMITS WERE DEEMED OUT OF LIMITS. THE SPRING TAB WAS REPLACED AND THE VIBRATION CEASED DURING SUBSEQUENT FLIGHTS.