Pax feedback to staff (TAP) that rear DTcar 'A3' train door open with loud bang.Staff (AMK) check ed and and confirmed fault. Pax feedback to staff (TAP) thatrear DT car 'A3' train door open with loud bang.Staff (AM ~~~~~ 3539 Pax feedback to staff (TAP) A3 train door open with loud bang. Staff (AMK) checked and and confirmed fault.  3539 A3(LHS & RHS) door leaf roller pitted - Replaced. Tested door operation - OK. Door GAuge, open/close timing, cushion speed - OK. Cleaning of J-rail done. During door testing, no banging sound heard.    Sarma/ALan/Kamar/Lee PT 44931