Train doors at Front DT A4 door were notproven closed. TC recycled train doors once - ok. Fault rec ur at subsequent stations. Staff (SOM) assisted to isolate F ront DT A4 door in close position ~~~~~ Check above mention fault due to LHS/RHS roller faulty. Replaced both rollers done. Check push/pull resistance mating, DLS, DLS, DLD and FOD ok. Door cyclic test several times ok. Done by Saini/Haslan.  01/09/22.