@xNYARLx you should open a new topic instead commenting on a post from four years ago. Please provide the information requested at: https://retropie.org.uk/forum/topic/3/read-this-first

Only lr-picodrive supports multi-disc games. Are you using that emulator for your multidisc games? Details about the Sega-CD emulators can be found in the docs here: https://retropie.org.uk/docs/Sega-CD/