Rear DT car 'B4' train door was not proven closed. TC opened and closed a few times to clear fault.  ~~~~~ #3629-A4 door unable to duplicate in the depot. Further checked PTU download, door gap, roller, door lock device, push pull gauge are ok. Repeated door fault-replaced door operator and send for bench test. Already DCP swapped to B3 door. ER and fault trace was downloaded. Door operator s/o-Old s/n: 1504W02000S001 New s/n: 1411W020011S002B Not: 2134816 raise to RSW. Done by Kumar/Jack/Sateesh/Koh. 25/02/20.