Train doors at car 3536 were not provenclosed. TC opened and closed a few times but fault persisted . Staff (CCK) assisted. 'A2' door at car 3536 isolated in cl osed position. ~~~~~ Check and found A2 door actuator metal ring at push back mechanism disloged-replaced door actuator. Function test door open/close ok. Door gauge test 10/20mm ok. Door static test ok. Downloaded ER in PTU006. Door actuator s/n: Old-100 037. New-100 495. Not: 2237167 raised. Done by Sanip/Faddzal/Koh. 08/01/21.