As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFT CARGO DOOR WARNING LIGHT ILLUMINATED AT START OF TAKEOFF. ABORTED TAKEOFF AT 50 KNOTS. FOUND PULL LANYARD JAMMED IN LOCK ROLLER PREVENTING THE DOOR FROM FULLY LATCHING. REMOVED LANYARD AND OPERATED DOOR PER AMM 52-31-00. OPERATIONAL CHECK GOOD. AIRCRAFT WAS GROUNDED.