WordPress shows // in URL for template page

I stumbled across this problem today. Only one page of a wordpress template has this really strange URL

http://www.mysite.nl/folder-x/%ef%bb%bfsander-john-en-marie-cecile/

None of the other files that use this same template file have this strange URL

http://www.mysite.nl/folder-x/ilonka-meisje-zonder-hoofd/

I read somewhere that this has something to do with a UTF-8 BOM but wouldn’t that then be across the whole template? There is no extra script being used on this page. It’s just a normal txt wordpress page.

I disabled the plugins that could interfere what I have red, but this didn’t help. Any help would be much appreciated.

Thanks.