As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING REMOVAL PROCEDURE OF THE #1 ENG. PNEUMATIC INTERSECTION MANIFOLD DUCT, FOUND 5TH STAGE BLEED AIR CHECK VALVE TO INTERMITTENTLY STICK OPEN. GROUNDED - YES. REMOVED AND REPLACED BLEED AIR CHECK VALVE OF THE #1 ENGINE PER B737-900 AMM 36-11-02, LEAK CHECK GOOD.