As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INSPECTION TYPE:N/A ATB - DUE TO CABIN ALTITUDE. AFTER ACCOMPLISHING THE QRH PROC CABIN REMAINED UNCONTROLLABLE. PERFORMED PRESSURE CONTROLLER BITE PROCEDURE FOUND NR 2 LOW IN FLOW FAULT FIM 21-31-00-815-803/REF TS-B767-2150-00007 FOUND LEFT PACK "LO" FLOW 25% LESS THAN RIGHT PACK. REMOVED & REPLACED LEFT PACK FLOW CONTROL AND S.O. VALVE REF AMM 21-51-01-401. AFTER REPLACEMENT.