Train doors at Front DT car train door were not proven closed. TC recycled train doors a few times t o no avail. Staff (AMK) checked and feedback the Front DT ca r, all A side train doors was fully opened and unable to clo ~~~~~ Train doors at Front DT car train door w #3645-A/S door unable to close due to DLCBA tripped.Checked DCP for any stray voltage-ok.Connected to DCP using PTU to check door operating check ok.All doors checked ok.DCCIBA normalise,door cyclic check ok.Postulate TC acciental tripped DCCBA when changing shift. Checked by Ashwin. 05/12/22