Hi again,
that issue is solved as one of the WPMUdev staff developer solved the issue on their plugin, they added
global $wp_query;
to a function
and replaced :
get_queried_object_id()
with :
$wp_query->queried_object_id
in the same function
(WPMUdev is going to release an update of the Pro Sites plugin I guess, for details, see this topic’s comment http://premium.wpmudev.org/forums/topic/pro-sites-incompatibility-with-bbpress?replies=15#post-234125)
I come back here to inform about it, in case someone else encounter the same issue (I saw a lot of “page not found” issues while searching BBPress forums), then it would maybe help to see which kind of code made conflict?
(I don’t know, I’m not a coder)
of course I still do not understand purely on BBPress how is it possible to have 2 possible permalinks for 1 subforum
either : example.com/forums/forum/level1/level2
or : example.com/forums/forum/level2
both url work, and this is not standard I think, anyway…
in any case, this issue is solved for me
ok, so as this worked for me I cannot help you more 
I’m sorry
maybe a permalink/htaccess problem?
Cheers
Hi @Everton
not sure I understood you correctly, and maybe you solved that since last week …
well I wanted the same thing (insert the bbpress forum index, in a standard WP page), thus thought I could insert a shortcode to call the forum, in a normal page
I created a page called “forum” (whatever you want there) and inserted [bbp-forum-index] in it,
all the available shortcodes are listed here : https://bbpress.org/forums/topic/bbpress-20-shortcodes
cheers
