Slight pause when using aux cable and unlocking samsung galaxy j5

[Tbugg190594]

Hi within the last week my phone running android 5.1.1 has whilst being used with an aux cable in offline mode begun to have a slight pause of 1-2 seconds when unlocking the phone. I have cleared all cached data in all apps, reinstalled spotify and restarted the phone changed all phone lock settings and battery uses but no fix. . I have seen posts before of similar problems but their answer was to reduce volume but this doesn't seem to work either. Anybody know whats going on