As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE OPENING THE MAIN DOOR, VERY LOUD "BANG" FOLLOWED BY FULL WEIGHT OF DOOR. UPON INSPECTION NOTICED CABLE SYSTEM THAT ASSISTS DOOR WAS SLACK. COULD NOT IDENTIFY IF CABLE WAS BROKEN OR JUMPED TRACK. INSTALLED NEW BALANCE CABLES ONTO BALANCE DRUM IAW AMM 52-13-22/400. PERFORMED MAIN DOOR OPENING SPEED ADJUSTMENT IAW AMM 52-10-00-820-804-A. ADJUSTMENT SATISFACTORY. REINSTALLED ALL ACCESS PANELS AND LH SIDE LEDGE.