I think it happens when you play in 50Hz only. Try turning deflicker off, switching to 60Hz. It should be fixed, and you can then go back to 50Hz and it should still be alright.
I've seen a few sites mainly stockholder circlejerk blah blah sites talking about it....but ND Twitter has said nothing and Atari has been as well...I'm wondering if this is a fake story to get Atari stock up