my volume knob is haunted

[Demolitionman]

I have a vintage roland jc 55,in really good condition,but the volume goes up and down on its own,can anyone give me and idea on why and maybe a how to to fix it? thanks

[Enzo]

Plug a spare cord from send to return on the efects loop jacks - does that help?

[52 Bill]

Also, when you rotate the volume control is the transition smooth or does the volume jump up and down?