TC reported Rear DT train doors were notproven closed. TC reported train door B3 had some door issu e. Recurred at YWT, staff KRJ isolate door in closed positio n ~~~~~ Checked and no FOD found on guide rail. Clean J-rail & guide rail. Check door mating strip ok. Adjust door locking switch. Door close timing 3.3, opening 3.4. Door roller ok. ER download & fault trace ok.    Done by Saini/Zulq.  19/10/20.