TC feedback DIR intermittently blinkingsince BGS WB but TC unable to see which car as there is no i ndication. Staff (OTP) check rear cab and feedback all doorsproven closed. Afterwards Train EB applied withDIR illumi ~~~~~ 3545 - TC feedback DIR intermittently blinking since BGS WB but TC unable to see which car as there is no indication. Staff (OTP) check rear cab and feedback all doors proven closed. Afterwards Train EB applied with DIR illuminated.  3546 B/S cab door found not properly closed & DIR lit. Found the s/w rod was obstructed by double latch, preventing cab door latch from latching fully on the double latch. Function check on all saloon doors - OK. #3546 B/S cab door was removed for filing/grinding the s/w rod to reduce its height by 3mm. Replaced the cab door cabledue to significant wear/tear(side finding). Re-installed cab door & function check - OK. S/w rod able to clear double latch with no obstruction. DIR able to extinguish when cab door was closed. S&C conducted function check & reset VOBC preventively. No abnormalities found.  Jonathan Koh WC 44967