As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ACFT RETURNED DUE TO THE LT ENGINE VIBRATION REACHING 6.0 UNITS. FLIGHT CREW ACCOMPLISHED QRH 7.24 PROCEDURE AND VIBRATION WAS STABILIZED IN 4.0 UNITS. MAINTENANCE DETECTED A CRACK ON FOUR FAN BLADES 1 INCH LONG AND 0.750 INCHES IN DEPTH, CRACKS OUT OF LIMITS IAW AMM 72-00-00. LT ENGINE REPLACED IAW AMM 71-00-02, TESTED CORRECT.