As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AD 2020-16-51 HAS BEEN ISSUED TO ADDRESS THE ENGINE BLEED AIR 5T H STAGE CHECK VALVE. C/W 5TH STAGE VALVE INSPECTION ON #1 ENGINE, REPLACED DEFECTIVE VALVE, IAW AMM 36-11-02 AND EA 3611-01438 REV B. COMPLETED VALVE, CHECK, F. THIS ENTRY TO REPORT 5TH STAGE FAILED TEST PER AD2020-16-51