As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WITH AIRCRAFT PARKED AT GATE, FLIGHT ATTENDANT HAD NOTICED A "DIRTY SOCK" SMELL AFTER APU BLEED WAS ON FOR ABOUT FIVE MINUTES. MAINTENANCE FOUND INTERNAL OIL LEAKING IN APU. OIL WAS COMING OUT OF PLENUM DRAIN. REMOVED AND REPLACED APU IAW JOB CARD 26L31049005. OPS LEAK AND BITE CHECK GOOD.