As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHEN REMOVING SWASHPLATE, MECHANIC FOUND NUT TO HAVE LOST TORQUE. (HAND TIGHT.) HAVE FOUND SEVERAL MAST NUTS ON 206L-3'S AND 206L-4'S MAST ASSEMBLIES THAT HAVE LOST TORQUE. BELIEVE THE CONTACT AREA BETWEEN THE MAST NUT AND THE BEARING INNER RACE IS TOO SMALL. THE 206B AND 206L-1 MAST NUTS HAVE A LARGER CONTACT AREA AND DO NOT CAUSE A PROBLEM. MODIFY MAST NUT FOR GREATER CONTACT AREA.