Train encountered BCU fault at Rear DT car. STBS was operated. ERS-15 ~~~~~ #3541 FC-308, 312, 330, 331, 314. Stuck brake when entering maintenance pit without 750vdc. Brake stuck at EM when on Coast. Found ACU solenoid exhaust port air leak. Replaced ACU and brake cyclic test ok. No recurrence of stuck brake. ACU- Old s/n: 1025-010.  New s/n: 1039-024. Not: 2187647 raised to RSW. Done by Koh/Samsudin/Gopal/Zulq.  09/8/20.