Train doors at car 3616 'A1' door did not opened. TC recycled train doors once - ok. Staff(MRB) chec ked and confirmed fault. Staff(MRB) later isolated the defec tive train door. Train doors at car 3616 'A1' door did not o ~~~~~ 3616 A1 Train doors door did not open. TC recycled train doors once - ok. Staff(MRB) checked and confirmed fault. Staff(MRB) later isolated the defective train door.  3616 A1 door FC initial operation error. TC cycled doors once. No FOD found, weather strip condition - OK. Push/Pull door was smooth. Cleaned J-rail/guide rail. Cycled doors & found DLD did not unlock. DLS red line flush, DCS actuating plate Distace, door gap 63.9mm - OK. Replaced DLD & function doors operation for open/close - OK.  Celine Tan 45062 DLD S/N : OLD : C151BDL14Z054 NEW : C151CDL16V045