As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW RECEIVED LOWER CARGO DOOR OPEN INDICATION. THUMPING NOISE ALSO HEARD BY CREW, AIR TURNBACK. REPLACED LT UPPER SPIGOT PIN ATTACHING 120 VU. ACCOMPLISHED A PRESSURIZATION TEST TO 4 PSI (ALPHA) P IAW AMM 05-53-00-0001. NO NOISE NOTICED FROM FLOOR STRUCTURE.