As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LOSS OF MR RPM INDICATION DURING RUN UP. SUBSEQUENT VISUAL INSPECTION OF HALL EFFECT SENDERS REVEALED NON CONFORMITY OF C908-1 REV K YOKE. DISASSEMBLY REVEALED FULL TORQUE ON ALL FASTENERS, BUT WEAR ON SPLINES OF YOKE AND PINION. ALL INFO SENT TO ROBINSON HELICOPTER COMPANY TECHNICAL SUPPORT FOR EVALUATION. ASSEMBLY HAD 500 HOURS IN SERVICE.