What was found
FLT 221, BOS-PBI. CREW REPORTED A DIRTY SOCK SMELL ON DESCENT STARTING AROUND 4000FT IN THE CABIN AND EVENTUALLY CAME INTO THE COCKPIT AROUND 3000FT. PACK 1 WAS ALREADY ON MEL. REPEAT ODOR EVENT. ACFT TAKEN OOS IN PBI FOR TS AND ECS DECONTAMINATION. DUE TO OIL LEAKAGE FROM APU FOUND DURING CABIN ODOR T/S STEPS, APU INOP ( APU SYSTEM ); R & R APU IAW AMM 49-11-11-000-004-001, SEE WO 1116000. MDDR 437714 CLEAR, PLACARD REMOVED, MX-4 UPDATED, MCC NOTIFIED."