TC reported Front DT car, door #3 did not opened. TIMS showed obstructed door at FDT car. Staff (AMK ) checked and confirmed FDT car, #3 door did not opened. SM (YIS) isolated the #3 door in closed position. ~~~~~ 3615 TC reported Front DT car, door #3 did not opened. TIMS showed obstructed door at FDT car. Staff (AMK) confirmed FDT , #3 door did not opened.    SM(YIS) isolated the #3 door in closed position.  3615 checked/found no FC. Unable to manually open door when DCP was tripped & interior door release handle was pulled. Checked DLD locking pin & manual isolation door lock pin & found no abnormalities. OPS 20 raised to remove door to check rollers & any FOD.  Lee JC 44756 3615 - To remove A3 door & check roller.  3615 A3 door checked/found door roller was damaged. Replaced the door roller & clean th eJ-rail. Security/function check - OK.  Alan/Lee PT/Shafie 44757