As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) BOTH INTERNAL FLAPPER VALVE APPEAR TO USE THE CHAMBER WALLS AS A MECHANICAL STOP, OVER YEARS OF USE, THE FLAPPER VALVES HAVE WORN A GROVE IN THE CHAMBER AND 1 SIDE HAS WORN THROUGH RESULTING IN 2 AIR LEAKS, CAUSING PRESSURIZATION ISSUES. IT IS ALSO WORTHY TO NOTE THAT BOTH VALVES ARE ALSO DEFORMED DUE TO CONTACT WITH THE CHAMBER SIDES.