The NES PPU has a sprite limit of 8. Some games, mostly unlicensed of homebrew games (such as Kart Fighter
or this Donkey Kong port
) utilize more than 8 sprites at the same time, causing sprite flickering. This can be fixed by increasing the sprite limit to 16. The RetroUSB AVS and Kevtris' Analogue Nt Mini/Hi-Def NES have such an option. I am not sure if such an option is necessary for compatibility reasons or if it is acceptable to permanently change the sprite limit from 8 to 16.
This file from the NES core would need to be changed: https://github.com/mist-devel/mist-boar ... /src/ppu.v