As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI ON FLIGHT 3504, BAD ODOR FROM PACKS. MAINTENANCE FOUND APU INOPERATIVE DUE TO LABYRINTH SEAL BAD. FROM LP 1216605 REMOVED AND REPLACED APU P/N 4501690A S/N OFF SP-E9875 49 S/N ON SP-E977516 PER TASK CARD APU CHANGE ALL CHECKS GOOD REMOVED. FROM DMR MXC NOTIFIED