Hi, reviving this post because I am getting the same issue and it is getting a lot worse:
Volume changes by itself every few seconds now... completely fades out, fades back in, jumps around. My Pod GO is completely unusable now. And I bought it in 2021, so not under warranty anymore :/
Happens even when volume pedal block is deactivated, therefore definitely not a "sunlight on opitcal sensor" issue.
I was on firmware 2.01.0, downgraded to 1.40 and still same issue.