TC reported rear M1 car "B1" train doorsnot proven closed. TC opened and closed train doors 3 times but to no avail. SM (ADM) checked and confirmed rear M1 car "B1" train doors slow in closing - assisted to push close f  ~~~~~ TC reported rear M1 car "B1" train doors     Check and found #1517-B1 door LHS door resistance very high ,further check found both door roller run against J rail and cause the r worn out,suspect roller over tighten.Door roller c/o ok.Observed carbody surround the J rail have rubber dust,clean up ok.Door actuator check ok.Door cyclic ok.Door static test ok.Door gauge 10/20mm check pass. Done by Kok/Faddzal.  21/08/21