Probably another big endian issue.
For easier tracking, i would generally recommend opening this kind of issue on the libretro fork's github, with all information you can gather : name of the romset(s), screenshot or video for gfx issues, recordings for audio issues, etc...
As a sidenote, don't bother reporting issues with killer instinct, it wouldn't run at full speed on ps3 anyway (needs a dynarec and we aren't gonna write a ppc mips3 dynarec).