TC reported of brake fault at Rear M1 car before entering ORC2. Fault self cleared upon arriving at station platform. ERS-12 ~~~~~ 1601 ER D/L & found 1601 stuck brake. Replaced 1601 ACU - Done. Brake pressure test - OK. 1601 ACU S/N : OLD : 1439/030. NEW : 1450/059.  Lee PT/Alcus. 03/06/2020.