Train encountered stuck brake at rear M2car at KRJ1. SM(KRJ) assisted to isolate rear M2 car BIC. ~~~~~ 2527 replaced ACU. Resealed STBS at 3528. Brake function test - OK. 2527 ACU S/N : OLD : 1008/001. NEW : 1310/134.  Hanafi/Azmi. 03/06/2020.