As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT PNEUMATIC CROSSOVER DUCT ISOLATION BYPASS CHECK VALVE FOUND FLAPPER LOOSE AND INTERNAL HOUSING WITH A CHAFE. THE CROSSOVER DUCT ISOLATION BYPASS CHECK VALVE WAS REMOVED, REPLACED, AND TESTED IAW AMM 36-11-05, REV 121. FOUND SATISFACTORY.