Tone knob not working at times

I have a squier affinity strat. Sometimes when I roll off the tone knob, it works fine and I can cut the high end, but then it randomly stops doing that and I am back to the cranked tone. It happens with both and knobs and all three pickups so I was wondering if it's a pickup problem, a knob problem or a wiring problem. I hope it's a wiring problem because I don't wanna know how much it will cost otherwise.