As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER DEPARTING, AIRBORNE, PRIOR TO REACHING CRUISE SPEED AND ALTITUDE. RT REAR DOOR CAME OPEN IN FLIGHT. ACTION WAS TO SLOW DOWN TO NEAR VTOSS AIRSPEED AND RETURN BACK TO DEPARTURE AIRBORNE. AFTER LANDING, DOOR WAS REMOVED AND ACFT INSPECTED, THEN RESTARTED AND RETURN TO HOME BASE. NO DOOR INDICATION LIGHTS CAME ON. IT APPEARS THE DOOR WAS IMPROPERLY CLOSED.