Train EB was applied when departing TNMEB. Released EB - ok. Proceeded in Auto mode to next station . TC reported A-side cab door was slightly ajar. Opened and closed the cab door - ok. ~~~~~ 3501 Train EB was applied when departing TNM EB.    Released EB - ok. Proceeded in Auto mode to next station. TC reported A-side cab door was slightly ajar. Opened and closed the cab door - ok. OE Depot check.  3501 found cab door latch screws loose - retightened. Function check cab door operation & found cab door cable broke. Cab door latch unable to unlock using the handle. OPS 20 raised to replace cable.  Lee JC 44644 To replace 3501 A/S i-hook cable.  3501 cab door cable replaced. Security/function check - OK. Cab door open/close cyclic test - OK. No DIR lit up when cab door was closed.  Alan/Lee PT 44616