Basically a power off fresh boot and everything is fine, after starting the RTG mode flickerfixing gets glitchy and unreliable.
I’ve noted some demos also have a black screen as some demos flip between modes quickly, or just whatever overscan sillyness they’re doing trips it up.
Hi, thank you very much for the detailled video. So far I would say it is a rather unusual issue. My hunch is that it could be EMI interference being picked up by the scandoubler cable, and those glitchy lines are when the HSYNC signal is slightly disturbed in those lines. I can give some recommendations for flat cable chokes (ferrites) but first maybe I could ask you to do some experiments of pulling/twisting the cable a bit just to see if that changes those glitches in any way. You could also substitute a longer IDE cable for example.
OK, maybe there’s just something up with your specific card. I’m sorry for all this trouble. If you write a quick note referencing this thread to support@mntre.com we’ll get your card shipped back to us and can send you a different one.