Hey guys just got back from practise and Im worried I use a Big Block 750 with the standard footswitch for mute and overdrive. I noticed that whilst the overdrive function works fine, lights come on etc. The mute does not, no lights and no mute What could this be ? Dodgy Footswitch or amp ? Its only 3 months old ! I have ruled out the cable as the overdrive works fine ? Any ideas ?