As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLAPS STARTED TO EXTEND, THEN FAILED TO EXTEND ANY FURTHER. FOUND THE FLAP ACTUATOR SPROCKET DRIVE SHAFT SHEARED WHERE IT COMES OUT OF THE GEARBOX. IT APPEARS THAT IT SHEARED BECAUSE THE INNER SPROCKET PIN HOLE IN THE DRIVE SHAFT HAD BEEN CROSS DRILLED. THE FIRST HOLE APPEARS TO HAVE BEEN DRILLED OFF CENTER, SO ANOTHER HOLE HAD BEEN DRILLED AT 90° TO THE FIRST HOLE THUS WEAKENING THE SHAFT.