and to make it persist through restarts, I had to manually edit system/recalbox.conf and change all

snes.core=snes9x10 to snes.core=snes9x

@bad_gambler Hello, I had a similar issue (if I understood correctly)

So after a factory reset, it was still not working, so I went to Advance Emulator Settings > Snes

And here, I saw that the default core was Snes9x2010 (or something like that). I put it back to Snes9x default, and then it works.

I hope I'm clear enough, if not do not hesitate to ping me, I'll try to give clearer instructions

Good luck!
Ben