There is a problem with the routing system of the forum server. Let me explain:
when you go on this page for example:
http://projectdxxx.me/forum/board/id/6
it will only display English messages. OK
if you want to display the messages of all languages, you go there:
http://projectdxxx.me/forum/board/id/6/lang/any
But, if you want to go from the first page of the example above (using the "all languages" link) by clicking the "next thread" button. It will lead you to this page:
http://projectdxxx.me/forum/board/page/2/id/6/

See? The "/lang/any" option has disappeared, leading us to a blank page.

Thank you for reporting the bug.
I fixed the bug.