As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, AT 5000 FEET, FLAPS ON EICAS WITH CONFIG WARNING HORN. AN EMER WAS DECLARED & THE FLIGHT RETURNED TO FIELD. WARNING & LIGHT WERE INTERMITTENT & WARNING CONTINUED UNTIL LANDING. ACFT WAS REMOVED FROM SERVICE. FOUND FSEU FAULT, LT FLAP STAB POS NR 27-51018. REPLACED FLAP STAB POSITION MODULE M838. ALL TEST PASSED IAW 27-58-11. OPERATIONALLY CHECKED OK.