As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURN BACK, ON CLIMB NR 4 LEFT LEADING EDGE FLAP GROUP WOULD NOT RETRACT PNEUMATICALLY. THE GROUP WAS ALREADY ON DEFERRAL FOR BEING INOP ELECTRICALLY. CREW DUMPED 69000 KILOS OF FUEL. UPON RETURN MAINTENANCE REMOVED AND REPLACED NR 4 PDU, ALL OPS AND LEAK CHECKED OKAY.