Posts With Numeric Titles Broken

Hello,

I set the default permalink structure and everything works fine (with category base of “lyrics”). I set the permalink structure to this: /%category%/%postname%/ (same category base) and any post that has an all numeric title, eg. a post with the name of 4321 gives a 404 error. The structure of the link looks like it should…. (example.com/category parents and children/post title/) Any ideas why?

Thanks.