I have a Category that I have titled differently from the Category URL; when making a post it appends the bottom of the post with #Tag Title, but the link is site.doman/category/Tag-Title not site.doman/category/TagURL, so all of that caegory 404s if going to the #tag in the post.
Workaround is unify title with URL work, but in this case I wanted a three word title, but a one word category subdirectory.