As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHIP 5643 BOTH PACKS PRODUCE A HEAVY MUSTY SMELL, MOST NOTICABLE WHEN SWITCHING PACKS FROM ENGINE O APU BLEED AIR AND VICEVERSA. CORRECTIVE ACTION: T/S FOUND OIL CONTMINATION AT HEAT EXCHANGER - LT AND RT. REPLACED LT AND RT SIDE ECS BAY PRIMARY AND SECONDARY HEAT EXCHANGERS REF B757 AMM 21-51. REPLACED RECIRC FAN. C/W OIL CONTAMINATION REMOVAL.