[Typo3] Pagetype 'External URL' doesn't seem to work with RealURL

[Robert Markula]

Hello everybody,
I've got a page with the URL http://www.domain.tld/youth/. In this page 
there is another page (Pagetype: 'External URL') which links to 
http://www.domain.tld/board. But on the frontend it still links to 
http://www.domain.tld/youth/forum (forum is the name of the external url 
page).

What can I do so the linking on the frontend is correct?
I'm using RealURL and Typo3 3.8.

Regards,
Ro