ECB activated at rear M2 car. Staff(ORC)assisted to reset ECB. Staff(ORC) feedback rear M2 B4 door did not open.Train taken out of service at JUR and replace ment train launched from UPD. ~~~~~ 2644 ECB activated. Staff(ORC) assisted to reset ECB. Staff(ORC)feedback 2644 B4 door did not open. Train taken out of service at JUR and replacement train launched from UPD. CE : 2644 checked all ECB ok n B4 did not open with sticker.  2644 B4 door FC 992. Door leaf unable to push opened. Further check found RHS door leaf outer roller delam. Replaced rollers for both door leaf. Clean J-rail and guard rail as preventive measures. Door gap 63.5mm. Door cyclic test OK.  Kamarul/Shafie/Sarma 45403