Corrupted Mod Config File (NightConfig ParsingException: Invalid character)

What the log looks like

com\.electronwill\.nightconfig\.core\.io\.ParsingException: Invalid character '
ConfigFileTypeHandler\$ConfigLoadingException: Failed loading config file [^\s]+\.toml.*com\.electronwill\.nightconfig\.core\.io\.ParsingException

How to fix it

1. Find the line in your crash report starting with `Failed loading config file` to see the exact `.toml` filename and whether its type is `COMMON`, `CLIENT`, or `SERVER`.
2. If the config type is `COMMON` or `CLIENT`, open your Minecraft instance folder, go into the `config` folder, and delete (or move to your desktop) that specific `.toml` file.
3. If the config type is `SERVER`, go into `saves/<Your World Name>/serverconfig/` for singleplayer (or `<world>/serverconfig/` on a dedicated server) and delete the named `.toml` file there; also check `defaultconfigs/` if the file exists there.
4. Relaunch Minecraft or start the server so the mod automatically generates a clean default `.toml` file.
5. If you want to customize the settings again, edit the newly generated file carefully in a plain text editor and make sure every key has a valid `= value` without stray line breaks.

Check your own log