What was found
DURING APPROACH INTO RSW WITH FLAPS 30 SELECTED, FLAP GOT TO 27 DEG THEN STARTED RETRACTING AUTOMATICALLY TO 20 DEG. AIRSPEED WAS AT 155 KTS. RECEIVED FLAP DISAGREE MESSAGE WHEN THIS HAPPENED. DID NOT GET -FLAP LOAD RELIEF- EICAS MESSAGE. ABORTED APPROACH. PERFORMED GO-AROUND AND ALTERNATELY EXTENDED THE FLAPS. MTC FOUND NO RELATED FSEU FAULTS. REPLACED FSEU AND RT ADC AS PRECAUTION.