Train EB was applied while departing station in Auto mode. ATS alarm showed CBTC EB applied due to o bstructed motion detected. TC confirmed no circuit breaker t ripped and no other fault indications. Thereafter, TC opened ~~~~~ 3521 EB applied departing station in Auto mode. ATS alarm showed CBTC EB applied due to obstructed motion detected. TC confirmed no circuit breaker tripped and no other fault indications. CE: T233 3522 No recurrence Of EB applied. No abnormality. OE request to download ER and check for cause of obstructed motion. Confirmed in LDC obstructed motion occurred.  3521 FC (BCU release Fault). ER showed stuck brake. Swapped ACU from #3521 to #3522. Replaced new spare ACU on #3522. Swapped BCU from #1521 to #3521. Replaced new spare BCU at #1521. Brake cyclic test & brake function test - OK. No residual pressure @ COAST. Limited movement & depot shunting - OK. Wheel diameter #3521 = 830mm, #1521 = 812mm. BRER on #3522 - OK. Performed cab door mod on all 4 cab doors  Sarma/Shafie/Kamarul/Anand/Lee PT 44876 ACU S/N (After Swapped) : #3521 : 1024/005 #3522 : 1311/060 (faulty)         1250/051 (NEW) BCU S/N (After Swapped) : #1521 : 1816155 (Faulty)         1809060 (NEW) #3521 : 1812096