Reply to fader problem

so i was just messing around with my s4 and noticed my fader for deck A was being a little bit weird, when i'd turn it all the way down the sound would still be going and the sound would get loud and then quite so i calibrated the faders and still had the same problem also when i used a gater and turned the volume all the way down the gater would still keep going

then i noticed if i took off the plastic peice on the fader and moved the metal thing around i could get it to work and now its working properly but when i push the fader all the way to the bottom, if i push to hard i get a bit of music coming through

if anyone could help that would be amazing

thanks!