: Ensure your ROMs match the MAME 2003-Plus core version; using standard MAME 0.78 sets will work for ~95% of games, but you'll miss out on the "Plus" additions and bugfixes.
: Clones require the parent file to be present in the same folder to run. Merged Sets mame 2003-plus reference: full non-merged romsets
By adhering to the convention with a correctly versioned set, you will achieve the highest possible compatibility with MAME 2003-Plus across RetroArch, Lakka, RetroPie, and other libretro-based emulation platforms. : Ensure your ROMs match the MAME 2003-Plus