How can a misconfigured `jupyter_notebook_config.py` file lead to a '500 Internal Server Error', and what are common misconfigurations to check?

A misconfigured `jupyter_notebook_config.py` can prevent the Jupyter server from starting or operating correctly. Common misconfigurations include incorrect file paths, invalid syntax in the Python configuration file, specifying non-existent themes, or incorrect SSL/authentication settings. To troubleshoot, first locate your config file (usually in `~/.jupyter/` or by running `jupyter notebook --generate-config` to find its location). Temporarily comment out recent changes or back up and delete the file to allow Jupyter to start with default settings. Then, reintroduce changes one by one to identify the culprit.