TIMS showed 'B4' train doors at the Front M1 car in isolated status. TC while changing end, confirme d said 'B4' train doors isolation indicator blinking momenta rily.Train scheduled UPD withdrawal. ~~~~~ 1644 TIMS showed B4 train doors in isolated status. TC while changing end, confirmed said 'B4' train doors isolation indicator blinking momentarily. Train scheduled UPD withdrawal.  1644 B4 door FC 992/986/980. Swapped #1644 B4 DCP with #1644 A4 DCP. Swapped #1644 B4 Door Isolation Device with #1644 B3 door. Further investigation found #1644 B4 RHS door roller delaminated. OPS 20 raised to c/o #1644 B4 RHS door roller.  Sugu/Lee PT/Kamarul 45130 DCP S/N : (after swapped) #1644 B4 : 1508W020021S043 #1644 A4 : 1508W020021S041 Door Isolation Device S/N : (after swapped) #1644 B4 : C151BIL157034 #1644 B3 : C151BIL157053    To C/O door roller.  1644 B4 door isolated. FC 992 (B4 door operation timeout) & FC 996 (B4 door open in motion). Checked/found #1644 B4 door RHS outer door roller delaminated. Replaced outer door roller, cleaned J-rail/guide rail & no FOD found. Door gap 63.9mm, weather strip condition, door cyclic test, door open/close timing - OK. All doors proven closed & no DIR lit up.  Sarma/Alan/Aliff 45130