As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TAIL ROTOR GEARBOX CHIP DETECTOR HAS ILLUMINATED IN FLIGHT. THE GEARBOX WAS SUBSEQUENTLY REMOVED FROM AIRCRAFT, REPLACED WITH SERVICEABLE UNIT AND AIRCRAFT WAS RETURNED TO SERVICE. UPON DISMANTLING OF THE GEARBOX IT WAS DISCOVERED THAT THE SEALING LIP WORE THROUGH ALLOWING THE TENSION SPRING TO CONTACT WEAR SLEEVE, RESULTING IN THE GENERATION OF METALLIC PASTE/SLUDGE.