TC reported intermittent brake fault atrear M1 car and train had slow pickup at some stations. TC p erformed rake status check at BDL2 but did not reflect any s tuck brake. ~~~~~ TC reported intermittent brake fault at #1683 Fault code 309 x 3 fault only at 1683 other car no BCU PWM fault.Replaced BCU .Function brake test ok.BCP within criteria.To monitor at M/L for fault occurance. BCU:- Old s/n: 14-49-101 New s/n: 18-47-408 Not: 2434343 raise to CSC. Done by Saini/Haslan. 10/11/22