As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: ON DESCENT, AT IDLE POWER, STRONG MUSTY SMELL IN CABIN WHICH REMAINED UNTIL SHUTDOWN. SMELL DISSIPATED WHEN ENGINES SHUT DOWN, APU AIR NOT USED. SMELL RETURNED WHEN EXTERNAL AIR HOOKED UP. MAINTENANCE FOUND THE APU OIL COOLING FAN LEAKING AND REPLACED IT PER AMM 49-52-51. (AALA202403015471) ALSO FOUND THE #2 ENGINE FAN AIR VALVE TEMPERATURE CONTROL THERMOSTAT DAMAGED AND REPLACED IT PER AMM 36-11-43. (AALA202403016319) MAINTENANCE ACCOMPLISHED A DECONTAMINATION OF THE ENVIRONMENTAL CONTROL SYSTEM PER TASK CARD 26L000021014. A SATISFACTORY LEAK / OPERATIONAL CHECK WAS ACCOMPLISHED WITH NO DEFECTS.