Hum when touching strings but a little different

Hi guys. I am currently experiencing a problem with my Kramer Pacer Custom 1. When I touch the strings the guitar hums. Now you would think that this would be wiring the hot and ground the wrong way round, however the guitar has not had any wiring mods for the last 2 years since I re-wired it and has been played nearly every day since.

The problem started when I turned the volume up, it would begin buzzing and would stop if I gave the volume nob a tap. The pot has a smooth action and no crackling. Now it just buzzes all the time. I have looked inside to see if there are any wires shorting out on each other but I can't see anything that would suggest this. Do you think it may be a bust pot?

Thanks for your help.