bbPress.org

Could be an issue with theme compatibility in bbPress. To get around that make a bbpress.php file in your theme.

Getting Started in Modifying the Main bbPress Template

You can see what WordPress conditionals affect what bbPress pages by using the test that is explain in this ticket from the user. Or you can check the theme compat file in bbPress.

https://bbpress.trac.wordpress.org/ticket/2723