As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF IN IAD CABIN ALTITUDE WENT ABOVE 10,00 0' RAN QRH PROCEDURES CABIN ALTITUDE WENT TO 11,500' WENT ON O2 RETURNED TO IAD. NOTICE FORWARD ENTRY DOOR WAS NOT SEATED PROPERLY OPEN AND SECURED DOOR SEVERAL TIMES, PERFORMED FORWARD ENTRY DOOR INSPECTION REF: M/M 52-11-001-6 CHECKED NORMAL. A/C OK FOR SERVICE.