As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ANNUAL INSPECTION, FOUND NR 4 CYLINDER LOW COMP. (170 HR SMOH). INVESTIGATION FOUND TOP COMP RING BROKEN AND UNUSUAL WEAR ON RINGS. RINGS WORN TO A BEVEL EDGE DOWN OVER RING LANDS. CHECKED ALL CYLS AND FOUND SAME WEAR AND SOME BROKEN RINGS. ENG HAD BEEN OVERHAULED WITH CERMA CHROME CYLINDERS.