Re: Problem with limiting posts per page
I’m not sure why this would happen, especially on the default theme.
I would recommend two things:
1) First, try disabling your plugins to see if that helps at all. If it does, enable one plugin at a time to see which plugin is causing the conflict.
2) If that doesn’t work, try this plugin?
https://bbpress.org/plugins/topic/front-page-topics/
I use it on all my sites, and it’s been great…
Good luck!