TC reported train stopped in-between station CCK NB to BGB NB momentarily. TC also reported TIMS sho w RM1 BCU fault however fault self cleared and train was abl e to proceed to BGB Station. ~~~~~ #1656 Found ACU hunting with heavy air leak from solenoid coarse exhaust when MCH is at coast position. Replaced ACU and carried out brake cyclic/function test-ok. Not: 2120169. ACU-New s/n: 1403-002.  Old s/n: 1523-120.    Done by Kumar/Jack/Koh. 10/01/20.