I've been reading countless threads of people experiencing artefacts with various AGA Indivision models.
Then I saw a Youtube video about a French guy who has the Mk1, then upgraded to the Mk3. He noticed that the artefacts went away by bracing his Indivision with a home-made "clamp"
I see you coming with your pitchforks yelling "no! don't do it" but it's an undeniable fact that the artefacts completely go away when I apply a bit of pressure with my thumb on top of the Indivision.
So save from building a brace like that, what else can I try? Cleaning the contacts with Alcohol? Because the issue is obvious, some contacts are not strong enough on the chip.