As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMOKE IN CABIN AT DISPATCH TIME APU LOAD CONTROL VALVE WOULD NOT OPEN AFTERWARDS. SUPPLEMENTAL DATA UPDATE, SEALS ON THE OIL BREATHER FITTING HAD WORN AND OIL WAS LEAKING EXTERNALLY INTO THE EXHAUST. ALSO, THE AIR/OIL COMPRESSOR SEAL AND THE TURBINE SEAL WERE WORN. THE APU WAS REPLACED.