New install NES issue

First, thank you to all who have contributed to this project. the install was seamless and easy.
I put my nes roms in the appropriate folder, configured the controller and started up a game.
All my nes games are running at 1/2 speed. The sound is there, and the game works, but I can't really play it at this speed.
My pc is a small one with a celeron processor. However, I know it's enough for nes games, as I have had retropie working on a debian install on this same pc with no speed issues. The processor is only at 29% as well, so I don't think it's my hardware. It's some setting in retroarch I'm assuming, but I don't know what it could be.

Thanks

Hello

In the settings, have you try to change core selection ?