As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHIP 3258 - FUME - WHILE PARKED AT THE GATE THE FLIGHT CREW BOARDED THE AIRCRAFT AND BEGAN VARIOUS PREFLIGHT CHECKS. THE AVIONICS VENT SYSTEM WAS ON MEL AND UPON START OF THE APU A SMOKY HAZE AND DIRTY SOCK ODOR WAS REPORTED BY THE FLIGHT ATTENDANTS IN THE REAR OF THE AIRCRAFT. APU PLACED ON MEL. CORRECTIVE ACTION: APU WAS REPLACED LOG 0774334 08OCT19.