As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE DES FROM FL310 TO FL290, NR 3 ENG VIBE LIGHT ILLUMINATED. VIBES ROSE RAPIIDLY TO 3.5 CONFIRMED BOTH A AND B SENSORS. SHUT DOWN ENGINE PER POM. INSPECTED INLET AND EXHAUST, REMOVED AND INSPECTED CHIP DETECTORS, NO DEFECTS. LUBED FAN BLADES AND RAN ENG TO T/O POWER, ENG RUN GOOD. RETURNED TO SERVICE.