As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE ACFT WAS CONFIGURED FOR CRUISE FLIGHT AT 3500FT. THE STUDENT WAS INSTRUCTED TO REDUCE AIRSPEED TO MCA. AT ROUGHLY 90 KTS AIRSPEED, THE INSTRUCTOR HEARD A POPPING NOISE FROM BEHIND AND WITNESSED THAT THE PRIMARY LATCH FOR THE REAR DOOR HAD COME OPEN 50 PERCENT. HE RE-ENGAGED THE LATCH AND LANDED WITHOUT INCIDENT.