Screwy dithering on Genesis Plus GX

Whenever I turn on Blargg’s NTSC filter to composite, the dithering goes crazy like on this pic.

What could be wrong?

Are you using the core option?

Yes it is. I’ve also tried dithering shaders and I get the same results…

Well, I can’t really tell what’s going on in your image, but if you’re referring to it becoming a horizontal line, I think that filter only blurs on the horizontal axis…?