Train stopped with BCU stuck brake indication at front M2 car after departing DBG. STBS operated. Pa x disembarked at CTH. ~~~~~ RSD found 2555 ACU faulty causing stuck brake. Replaced ACU and brake functional tested ok. RSW found MOD3 ACU solenoid valve plunger seal degraded. Faulty MOD3 SV replaced. From MO 10769653     Downloaded ER fault trace to PTU006 shown #2555 encounter stuck brake.Fault confirmed,ACU brake slow release when B1 to coast-replaced ACU and function check ok. Carried out ACU fleet wide c/o on the following cars and function and cyclic test. Cars:    Old s/n:   New s/n:   Not: #2555    1037-057   1042-077   2170096 #3556    1016-003   1034-013   2170097 #3555    1020-002   1012-010   2170098 #1555    0004-055   1042-071   2170099 Done by Jack/Sateesh/Koh. 15/06/20