So, I'm asking this on behalf of someone else, but apparently this spesific game freezes on a screen or says "file could not be loaded please reinsert the cartridge and power off the system", I'm not sure, as I don't use flash carts, but is there a known workaround for fix for this game...
I took a look at the rail and noticed that the two last pins were soldered for some reason, luckly I still had the rail of my broken joycon so after I swapped them I was able to use it attached to the console