Train doors at rear M2 car 'B2' door were not proven closed. TC recycled train doors once - ok. Faul t recurred at NEW1, NOV1, and TAP1. SM (NOV) isolated the fa ulty train doors. ~~~~~ Train doors at rear M2 car 'B2' door wer     #2557-B2 door replaced V-packing for door close speed and door close cushioning.Final adjust door speed and cushioning to achieve criteria.Door cyclic 10x and 10-20mm-pass. Done by Koh. B.S.  13/07/21