TC reported BCU fault at front M2 car and came to a gradual stop when departing MRB2. TC operated ST BS and proceeded in ATPM to MSP2 to disembark. BIC isolated after TC changed ends at MSP Siding. ~~~~~ ER downloaded on PTU 006. Observed #2611 encountered stuck brake, BCP at B3 when all cars brakes released. Replaced ACU and brake cyclic/function test ok. #2611 ACU-Old s/n: 1528-128.  New s/n: 1516-108. Not: 2124987.    Done by Koh B.S. 28/01/20.