Cab door 'A' side opened by itself whentrain was moving. TC opened and closed cab door to no avail.TC have to hold the cab door while the train depart in auto . ~~~~~ 3568-Cab door 'A' side opened by itself when moving. TC opened and closed cab door to no avail. TC held the cab door while the train depart in AM. Thereafter TC mentioned there was an mentee TC on board that was able to assist to hold onto the cab door. Train was scheduled UPD withdrawal.  3568 A/S cab door found latch locking screw loose. Tightened the screw. Security/function check - OK. Latch overlapping clearance checked - OK.  Irwan/Syahid 44746