As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ATB - DIRTY SOCK SMELL AFTER TAKEOFF. RETURNED TO BOS. CORRECTIVE ACTION: FOUND APU COMPARTMENT CONTAMINATED WITH OIL FROM LEAKING OIL CAP. REPLACED OIL CAP PACKING. PERFORMED LEVEL B ECS DECONTAMINATION. RAN ENGINES AT IDLE AND APU WITH BOTH PACKS. NO SMELLS NOTED. HIGHEST P-TRAK VALUE ONLY AT 5K. REPLACED RECIRC FILTERS. HIGH POWER RUN GOOD. (9518658) AIRCRAFT WAS GROUNDED.