As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DURING DESCENT THRU 10000, THERE WAS A STRONG ACRID SMELL THROUGHOUT THE CABIN. THE ODOR WAS SLIGHTLY BETTER AFTER TURNING PACK 1 OFF. THE STRONGEST SMELL WAS NOTICED IN THE AFT OF THE CABIN. MAINTENANCE FOUND OIL LEAKING FROM THE APU DRAIN MAST FOR THE FUEL CONTROL UNIT / OIL LUBE MODULE. MAINTENANCE REPLACED THE APU OIL LUBE MODULE AND THE APU FUEL CONTROL UNIT (AALA202407021886). A SATISFACTORY LEAK / OPERATIONAL CHECK WAS ACCO0MPLISHED WITH NO LEAKS OR DOSRS NOTED.