As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
C106-5 AND C106-6 JOURNALS WORE INTO THE MAIN ROTOR HUB. THE HUB WAS SCRAP. SEVERE SHIP VIBRATIONS NOTICED WHEN LIGHT WEIGHT AND LOW COLLECTIVE INPUT. SUBMITTER STATED POSSIBLE CAUSE AS CORROSION ON JOURNALS WORE THE C648-1 BEARING MATERIAL AWAY UNTIL IT WORE INTO THE HUB.