Train door at rear M1 car not proven closed. TC performed platform duty to clear fault. ~~~~~ 1667 A4 door measure door resistance within criteria. Door open/close cyclic test - OK. Check door gap/roller & open/close timing within criteria - OK. No rubbing/sluggish movement - OK.  Selvan/Lee PT. 04/05/2020.  1667 A4 door operator swopped to 1667 B4 door. B4 door installed with new door operator. Swopped DCP from 1667 A3 door to A4 door. Function test - OK. 1667 B4 door operator S/N : OLD : 1601 W 0200015023. NEW : 1405 W 0200315001.  Selvan/Lee PT/Alcus. 05/05/2020.