Guitar pedal randomly changes tone to a fuzzy sound - how to fix it?

Question

I have a guitar multi-effects pedal (a Boss ME-70). Sometimes I have a tone dialed in, and then it randomly changes sound to a very fuzzy / fat tone. When it does so, a number (usually around 90ish) appears on the digit screen.

I can get the original tone back by switching tones, and then switching back again. For example I'm on tone 1, it goes to a fuzzy sound, switch to tone 2 (which is fine), switch back to tone 1 (it's fine).

The frequency of this appears to be random - it can happen a lot e.g. today every few minutes, or just once every ten minutes or so, or less frequent.

I have had this effects pedal for about a year, and I had no problems before a few weeks ago. It's second hand though, I don't know how old.

Two short video examples of this:

(happening with a more "metal" tone)

https://youtube.com/shorts/GzBSX2QrJRw (happening with a more "rock" tone - sorry, poorer sound quality)

Any suggestions of how to fix this would be welcome.

Answer 1

Probably a dirty switch or dirty pot, making a 'crackle' which is interpreted by the digital encoders as legitimate new information.

As it's second hand & well out of guarantee/warranty, the first DIY approach would be to get inside it & give all the moving parts, pots, faders, switches etc a good dousing in contact cleaner. Power off to do it, spray each one liberally then run it through its full motion a dozen or more times to help the cleaner sluice the dirt out, then spray again.
To be on the safe side, give it 24h to thoroughly dry out before re-powering.
Test before you reassemble.

Answer 2

Dissatisfying answer, but I completely unscrewed/unbolted the pedalboard, then put it back together, and after that it worked (I've played guitar with it twice over a few days and no problems). So maybe there was literally a screw loose somewhere.