As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON INSPECTION OF M/R MAST BEARING DUE TO METAL CONTAMINATION, IT WAS DISCOVERED THE BEARING HAD BEEN INSTALLED UPSIDE DOWN AND THE INNER RACE WAS DAMAGED BEYOND LIMITS. BELL INSTRUCTIONS ARE SPECIFIC ON THE ORIENTATION OF THE BEARING ON INSTALLATION.