TC reported that 'A' side cab door unable to open. TC used partition door to board the train. ~~~~~ 3558 A/s cab door magnetic s/w found loose.    Re-tightened loose magnetic s/w & adjusted catch gap. Security check - OK. Function check - OK. A/s cab door able to open/close. DIR indication lit up - OK.  Redzwan/Haiqal. 29/01/2020.