As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INSPECTION TYPE:NA*DIVERSION* AT FL 380 LEVEL ONE ALERT CABIN PRESS RELIEF CABIN ALT BEGAN CLIMBING WITH OUTFLOW VALVE CLOSED BEGAN DECENT DURING DECENT MASTER WARNING CABIN ALT LEVEL 3ACCOMPLISHED FIM 21-33-02-00 BLOCKS 1, 2, 5 & 8 FOUND INSULATION MATERIAL IN MIDDLE CABIN POSITIVE PRESSURE RELIEF VALVE REMOVED & REPLACED MIDDLE VALVE WITH REF TO MM 21-34-01-401 REF LOGPAGE 638040 ITEMS 2 AND 3 FOR FUNCTIONAL CHECKS ESR IPC 21-34-01-01