As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT NR 1639 - PHL - THE AIRCRAFT WAS RETURNED TO PHL AFTER THE NR 6 LEADING EDGE SLAT FAILED TO RETRACT. MAINTENANCE FOUND THE NR 6 SLAT ACTUATOR STUCK IN THE DOWN POSITION. THE ACTUATOR WAS REMOVED AND REPLACED AND LEAK AND OPERATIONAL CHECKS WERE GOOD. (Z)