I had an issue similar to what you describe, that gradually appeared, but prior to v3.01 coming out. In my case it was a hardware issue that was fixed under warranty - I’d had the unit for 10 months. your case may be different? but it does sound close to what I saw.
Wiggling the crossfader gently made the issue appear and dissapear, in my case.
the PRIME GO does not have the panel for direct access to the cross fader, the entire unit needs to be dismantled to get at it, which looks like a major PITA.
I had the same issue I sprayed it with an electronic spray called DEOXIT D5 and it fixed it immediately and I haven’t had any problems with it since.