As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HIGH N1 VIBRATION ON NR 2 ENG, N1 DROPPED TO 50 % & RETURNED TO NORMAL ABOUT 5 SECONDS LATER. PERFORMED GVI OF NR 2 ENG INLET, EXHAUST & FAN BLADES. INSPECTED FOR PRESENCE OF CHIP DETECTOR CONTINUITY, NO DIC FOUND. PERFORMED GND POWER RUN WITH CREW. NO DEFECTS NOTED IAW AMM 72-21-02 & 71-00-00.