As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW HEARD A SINGLE BANG NOISE. DECIDED TO CONDUCT PRECAUTIONARY LANDING. WAS LATER FOUND BY MECHANICS TO BE A LATCH FOR THE SLIDING DOOR THAT WAS NOT SEATED PROPERLY, THAT DUE TO AIRCRAFT VIBRATION RETURNED ITSELF TO IT'S SPRING-LOADED REST POSITION, CAUSING THE BANG.