As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE ENGINE WITH SUBJECT GEARBOX STARTED MAKING METAL ON MAINTENANCE RUNS AFTER ENGINE INSTALLATION. METAL FOUND ON GEARBOX CHIP PLUG. AFTER OPENING UP GEARBOX, FOUND UNIDENTIFIED METAL RING INSIDE. NO VISIBLE SIGN OF DAMAGE TO GEAR TRAIN. RETURNED GEARBOX, FOR FURTHER EVALUATION.