As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHIP 3161 - ATB/FUM - CREW ALERTED BY FAS OF FUMES IN AFT CABIN. RETURNED TO MCO. FOUND OIL RESIDUE IN APU INLET AND PLENUM MATING SURFACE. APU TO BE PLACED ON MEL FOR CLEANING. FOUND TRACE EVIDENCE OF OIL IN LT ACM. REPLACED ACM. DUE TO REPEAT EVENT, ECS LEVEL "C" DECONTAMINATION REQUIRED. REPLACED ACM, AND OZONE FILTERS. (LP 6997726)