Hi @pippoart. Nice idea but unfortunately this hasn't worked for me (UX1, Early 2013, Catalina 10.15.5), still get the exact same problem.
I started a ticket with line6 and they got back to me, here is what they said:
This is a macOS issue which appeared after the 10.15.4 update of macOS Catalina (not before on 10.15.3)
This problem is mostly linked to certain hardware only (older Macs up to 2012/13)
Unfortunately we can only recommend using macOS versions before 10.15.4, there's no information available at the moment about possible macOS fixes
So basically I'm dead in the woods :(