As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE ACCOMPLISHING FAN BLADE LUBE ON NR 2 ENG, T/C NR 78472010, FOUND CU-NI-IN COATING WORN BEYOND LIMITS ON NR 4 BLADE. GROUNDED - YES. ON NR 2 ENG S/N 658831, REPLACED FAN BLADES NR 4 AND NR 16. BLADE REMAPPING ACCOMPLISHED, REF B737-900 AMM 72-21-02-000-802-F00. VIBRATION SURVEY AND FAN TRIM BALANCE REQUIREMENT ACCOMPLISHED ON T/C 78472010.