As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE ROTOR RPM WARNING LIGHT BEGAN TO FLICKER, AT THIS TIME THE MAIN ROTOR RPM TACH ROTOR NEEDLE WAS ALSO OSCILLATING MAINLY TOWARDS A LOWER RPM. REMOVED, CLEANED, APPLIED STABILANT 22 AND REINSTALLED THE CANNON PLUG AND ROTOR RPM SPEED PICKUP. GROUND RUN AND PERFORMED AN OPERATIONAL CHECK FLIGHT WITH NO FURTHER DEFECTS NOTED.