Plugin producing raw script code visible to users

When the ‘post title’ checkbox is unchecked, there seems to be an error on the page which does not resolve until the post checkbox is unchecked. The error is a json file which is attached to the body tag.

Please check the option here: https://ibb.co/7GbxWjT