Train came to a gradual stop in AM mode3646, N at track circuit N771 with stuck brake indication at front M 2 car momentarily. Fault cleared subsequently and train proc eeded in AM mode to next station. ~~~~~ 2646 found FC 314. Replaced 2646 ACU. Security & function test - OK. 2646 ACU S/N : OLD : 1516-096 NEW : 1447-053  Sarma/Chan SW. 06/02/2020.