As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RPM INDICATION SENSOR RING FOUND BROKEN DURING ROUTINE INSPECTION. THIS SENSOR RING FITS UNDER THE VENT OF THE RIGHT MAGNETO AND PROVIDES ENGINE RPM INDICATIONS. APPEARS TO BE BROKEN DUE TO FLEXING/FATIGUE. PERHAPS A DIFFERENT SENSOR OR OTHER MORE SECURE MOUNTING OF SENSOR WOULD PREVENT SUCH FAILURES.