Well obviously something was installed or changed which is why I suggested clean test installs without anything else. There is no issue with the actual coding all my examples show exactly how things works.
Preferably you would use a secondary domain name and setup a whole new site root so there is no contamination from your main site.
Most hosts nowadays allow multiple site setups so it should not be a real big issue but at the very least you want to do clean test installs like say this with no mods Audi TÃ¼rkiye KulÃ¼bÃ¼ & Audi Forum Audi TÃ¼rkiye KulÃ¼bÃ¼ Galeri
Knowing your site worked fine just shows that whatever happened recently installed is causing your issue. You had to have installed vbseo
or new htaccess files redirects etc. This could be months ago if you never noticed this issue. How long have you had vbseo
I know you changed your url structure as your forum was installed in a directory called forum in posts here 7 months ago. It could be redirects you placed months ago after moving directories that could be causing this.