As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: LEADING EDGE SLAT POSITION FOUR REMAINED ILLUMINATED AFTER FLAP RETRACTION. CREW DECLARED EMERGENCY AND RETURNED TO PHL. REMOVED AND REPLACED #4 LEADING EDGE FLAP RETRACT AND EXTENDED SENSOR. OPS CK GOOD AMM 27-88-11