Lower Case Conversion not working

On our site when someone links to say /TIRED-dog/ it opens the page keeping the URL with uppercase. So it opens the /tired-dog/ page, but does not rewrite the URL to lowercase.

This is causing confusion with search engines who tell us we have two URLs when there is just one URL.

We have the setting convert to lowercase as YES. Is this a bug in our version? How to force lowercase?

Thanks.

Which Joomla version?