I have had loose lugs on pots that cause volume cut outs and noise!
Take a close look a pot...and you can see that the solder lugs are clamped like a heavy staple (USA, CTS pots) or are riveted (import pots) to the carbon control disc.
Take a look at the third part. A loose physical connection between the shiny lugs, and black control disc can create all manner of pesky volume/tone cut out and noise!
Tweaking a finger on these lugs to test their fitness while the guitar is amplified, might turn up a "bad pot". Put a plastic baggie on your finger to reduce the noise generated by your body. I do not recommend this for amplifier diagnosis.