Just a guess but have you tried waiting a while for the game to load? At least 90 seconds, let’s say.
There’s an option/feature with the emulator that runs Atomiswave where it copies the game into memory on load. I guess this is something the actual system does too (https://nicole.express/2021/sega-sammy-atomiswave.html) but anyway, it can take a decent amount of time given the size of the game (KoF Neowave) and the speed of SD cards or USB I/O.
Worth a shot!