TC feedback train unable to remain in AMmode when TC tried to switch to AM mode a few times. EB app lied in AM mode and train switched to 'OFF' mode.ATS Alarmshowed "CBTC applied EB due to EB Command/status mismatched  ~~~~~ 3556 D/L ER showed that DIR de-energised momentarily. SDIR remained energised & DOR was not energised. LDC Log showed that no door OPEN command was given. Measured #3556 COR6, DLR & SDIR relays. COR6 & DLR relays - Satis. Found SDIR coil resistance slightly high (5.1 kohm) & contact fluctuating (between 15 - 20 ohm). Replaced SDIR relay. All cab doors within MRC criteria. Cycled saloon doors, DIR able to extinguish.  Kwa ZY. 08/09/2022. Down UPD 08/09/22 - 13/09/22 Further Investigation.  3556 replaced DLR & COR6. Measured COR6 coil & contact - Satis. Cleaned M2-M2 coupler pins. Based on ER, train was in AM mode when fault occurred. Found that COR3 dropped causing ER to stop recording. Suspect COR6 dropped which caused door loop to de-energise based on LDC logs. COR in AM controlled by SIG relays. Referred to SIG to follow-up. SIG checked relays DTOR & conducted M/L test. M/L test - Passed. Notif 2417143 raised to SIG to 555/556 PPU due to DTO MRS dropped with EB at CHD TB1.  Kwa ZY. 12/09/2022.