As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT ALTITUDE NR 1 ENGINE OIL QUANTITY WENT TO ZERO AND OIL PRESSURE DROPPED INTO THE AMBER BAND. SHUT DOWN THE ENGINE AND RETURNED. OIL PRESSURE REMAINED AT 35 PSI FOR 40 MIN WINDMILL. INSPECTED, FOUND FITTING UNSECURED. THREAD DAMAGED. REPAIRED GEARBOX, INSTALLED FITTING AND OPS AND LEAK CHECK GOOD. ALL WORK PERFORMED IAW 737 MM 79-00.