As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEADING EDGE SLAT DISAGREE EICAS MSG WHILE RETRACTING FLAPS 1 TO 0 AIR TURNBACK TO JFK. T/S PER FIM TASK 27-51-00 FIG 104B AND 115 FOUND SWITCH S1 CONNECTOR AT FAULT. REMOVED AND REPLACED S1 SWITCH AS PER MM 27-51-29 ACOMP REQ, OPS CHECKS OK.