As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURN BACK AND EMERGENCY DESCENT DUE TO A PRESSURIZATION ISSUE. QRH PROCEDURES ACCOMPLISHED, EMERGENCY DESCENT TO 10,000 FEET WHERE CABIN RECOVERED. NO MASKS DEPLOYED. FOUND THE LEFT WATER SEPARATOR DISCONNECTED FROM FORWARD DUCT AND SEVERAL CLAMPS LOOSE. MAINTENANCE SECURED CLAMPS.