Train doors not proven closed at rear DTcar B4 door. TC opened and closed train doors thrice to cle ar fault. ~~~~~ L3 3682 ER showed DIR dropped. TC cycled doors 3x to be proven closed. FC showed #3682 B4 door close operation timeout 3x. Fault trace showed door obstruction detected at same gap of approx. 40cm 3x. No FOD found & no signs of wear marks caused by FOD. Checked J-rail/guide rail & found no abnormalities. Used scope to check the rollers condition - OK. Doors not wobbling during cyclic test. DLS red line flushed with surface for positive latching. DCS actuating plate distance satis when doors closed. Door gap within criteria when closed. Checked door motor current during opening/closing - satis. Postulate DCP intermittently faulty causing unable to be proven closed at same gap size 3x. Checked DCP connections & no abnormalities found. Replaced DCP, cyclic test - satis. TIMS door static timing test within criteria. DIR able to extinguish as required. #3682 B4 DCP S/N : OLD : 1602WO20021S032. NEW : 1701WO20071S016.  Lee JC/Celine tan. 10/03/2023.