As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOTS REPORTED UNUSUAL LOW FREQUENCY VIBRATIONS AND UNUSUAL CYCLIC PRESSURE IN FORWARD FLIGHT AND AUTOROTATION. UPON INSPECTION OF MR BLADE SPINDLE BEARINGS IN REFERENCE TO "TRACK AND BALANCE TROUBLESHOOTING" R22 MM SECTION 10.234 FOUND THE SPINDLE BEARINGS TO BE BRINELLED. POSSIBLE BEARING MANUFACTURING ERROR.