Just pulled out my original Nintendo from the closet, connected the EverDrive N8 to a Famicom to NES converter and everything worked like it should. Seems its just a conflict if the Hi-Def Nes HDMI firmware and the EverDrive firmware. That’s a shame, both devices do what they’re made to do, just not with each other, at least not for me.
I tried the same games, Ninja Gaiden and Super Mario Bros. 2. I dont know if its a mapping issue that those two games seem to share, and maybe games like them seem to share or what, but its worth noting. Those two games are the x factor.
I had a Nt mini (which I sold last year) and both of those games work perfect for me on my n8. I do know that when you put games back on sd card? (Seems like you've done it many times by your post) you should always reformat sd card without doing so can give errors and issues with games.