Hi, It's just mechanical as it does happen when it's not connected or plugged in. I'm sure lubing it would indeed stop the squeak, but I have seen comments elsewhere that this squeak is due to some of the shims not being properly installed. I don't want to invalidate the warranty even if I'm sure it is easily fixable. Unless a line 6 rep tells me it's OK that is.
I bought the FBV Express Mk II for my son about a month or so ago. It works fine in terms of sound, but it has an annoying squeak when he works the Wah pedal. Our usual solution is to crank the volume up but I kinda think this should only be temporary. :) If it's just a case of lubing the shims on the pedal shaft/axle I'm happy to do that provided it won't invalidate the warranty. Or does this indicate a fault and I should return it for a replacement? Amazon are usually pretty good with that sort of thing. It just seems a bit unnecessary if it's just some dry surface friction. Cheers.