As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNUSUAL AIR HISSING NOISE COMING FROM NEAR FLOOR AIR VENT AT 39ABC. FOUND APU DUCT CRACKED AFT CARGO COMPARTMENT LT STA 540. CRACK ON UPPER SECTION OF DUCT APPROX 1 INCH LONG BY APPROX 1-4 INCH WIDE. APU BLEED INOPERATIVE. WHEN GND START INITIATED, NO HISSING SOUND HEARD FROM CRACKED DUCT. REPLACED DAMAGED APU PNEUMATIC DUCT IN AFT CARGO PIT SIDEWALL. LEAK CHECKED GOOD. NO HISSING NOISE NOTED.