As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DFW - AIRCRAFT HAD A HAZEY LOOK THROUGHOUT THE ENTIRE CABIN AND THERE WAS A MUSTY TYPE SMELL. THE HAZEY LOOK BECAME VERY THICK AND THE SMELL GOT MUCH STRONGER. FOUND APU LEAKING OIL. REPLACED THE APU. SYSTEM GROUND CHECKED NORMAL OPERATION.