TC reported intermittent brake fault atFront M2 car. Brake status check-ok. Train performance -ok ~~~~~ 2526 TC reported intermittent brake fault. Brake status check-ok. Train performance - ok.  2526 ER D/L & found FC 308/312/331/332. BCP also abnormal on #2526. Swapped #2526 ACU with #1526 & #2526 BCU with #2525. Replaced #1526 with new ACU. Wheel diameter setting - Done. Brake function check & BCP within criteria. Brake cyclic test - OK.  Hanafi/Chan SW 44693 ACU S/N :      OLD            NEW 1526    :    1240/095       1037/048 2526    :    1037/055       1240/95 (from #1526)             (1037/055 sent to RSW) BCU S/N : 2525    :  1823187 (from #2526) 2526    :  1813107 (from #2525)