As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FWD CARGO DOOR ANNUNCIATION CAME ON AT FL 270 (CABIN PRESS DIF 7.0). CABIN ALTITUDE KEPT ON INCREASING AND COULD NOT BE MAINTAINED. RETURNED TO BAQ. THE SYSTEM AND DOOR WERE CHECKED FOR LEAKS, NO LEAKS. SELECTOR CABIN PRESSURE PANEL WAS CHANGED, TEST OK IN ACCORDANCE WITH AMM 21-32-00 PAGE 202-203, 21-00-00 PAGE 516 AND 52-31-00 PAGE 601.