What was found
(CAN) DURING SCHEDULED MAINTENANCE OF THE AIRCRAFT. THE FLAPS WERE SELECTED DOWN TO THE 40 DEGREE POSITION. DURING MOVEMENT OF THE FLAPS A 'GRINDING' NOISE WAS HEARD COMING FROM THE L/H INBOARD FLAP ACTUATOR. THE ACTUATOR BECAME VERY HOT AND WOULD CAUSE THE FLAPS TO STALL. THE AIRCRAFT HAD RETURNED FROM A TRIP APPROX. (1) HOUR PRIOR TO THE DEFECT OCCURRING. THE PILOT DIDNOT INCOUNTER ANY FAILURE OF THEFLAP SYSTEM DURING THE FLIGHT. A REPLACEMENT ACTUATOR WAS INSTALLE D AND NO FURTHER DEFECTS WERE NOTED.RECENT PROBLEMS WITH THIS AIRCRAFTS FLAP SYSTEM, WERE THE RESULT OF ACTUATORS FREEZING AT ALTITU DE. THIS IS OUR FIRST INCIDENT WHERE SUCH A FAILURE HAS OCCURRED.