Hi,
I had the same problem when I published a new page called Forum. I also tried to find a solution for this permalink problem and I found the following. Start with simple set up. Make a home page and a forum page. Make sure that the home page is static home page, see settings/reading. Make a forums page and make sure that your forum’s page permalink address just below the title ends /forums. There is also some other combination with those page and menu settings that might work, but it is important to check page and menu settings.
