Have you figured this out. I’m not sure what the error means, but I think that render_field_settings is looking for something like ‘text’, ‘select’, ‘radio’ or ‘textarea’, but I can’t be sure. There really isn’t any documentation on calling the function directly, at least not that I’ve found, it’s usually used inside the render_field method of a field type.
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users