'A4' Train doors at rear DT car were notproven closed. TC opened and closed a few times to clear fa ult. ~~~~~ 3537-'A4' Train doors at rear DT car were not proven closed. TC opened and closed a few times to clear fault.  3537 A4 door sensor plunger modified by NUS project found broken. Removed & returned to NUS professor.  Lee PT/Alcus 43894