As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HOUR METER ON TACHOMETER STOPPED RECORDING. OPENED TACHOMETER AND FOUND THE MAIN DRIVE GEAR CAME LOOSE ON THE SHAFT. THIS IS THE 4TH OCCURRENCE OF THIS PROBLEM ON THE EXACT MODEL TACHOMETER. MFG NEEDS TO ATTACH DRIVE GEAR MORE PERMANENTLY TO THE SHAFT. TACHOMETER RPM INDICATOR STILL CONTINUES TO OPERATE CORRECTLY.