RetroArch windowed vs fullscreen (A04)

I have never had an issue with the RetroArch menu. Only with the performance of specific cores under specific conditions. For example, with snes9x in full screen, with specific ROMs, I get a low framerate and audio stuttering. But the RetroArch menu works fine.

My basic steps:

  1. I updated the system in place:
  1. I installed RetroArch:
sudo apt install retroarch retroarch-assets