If errors are found, select "Apply Repair." The tool will attempt to rewrite the necessary boot data to the cartridge.
If you find yourself constantly needing to run repair utilities or re-add .3dsx files because they mysteriously vanish or corrupt, your SD card might be physically failing. errfix3dsx
If you need help tracking down the file or run into a specific error message while running the script, let me know you are using and what operating system you are running it on! Share public link If errors are found, select "Apply Repair