What was found
ON LANDING, GEAR DOWN AND FLAPS 20. WHEN FLAP HANDLE WAS MOVED TO FLAPS 25, RECEIVED A TE FLAPS DISAGREE EICAS AND AMBER TRAILING EDGE DISCREET LIGHT. EXECUTED A GO AROUND, FOLLOWED QRH AND LANDED. WHEN GEAR WAS EXTENDED ON SECOND APPROACH EICAS CLEARED AND FLAPS EXTENDED TO 25. REMOVED AND REPLACED THE NR 1 RVDT ON OUTBOARD SLAT PDU IAW AMM 27-81-11-4, FLAPS AND SLATS CHECKED GOOD IAW AMM 27-51-00-5-0 AND 27-81-00-5-0, OK FOR SERVICE.