Hi - I'm just throwng this out there . .. I had a brief problem initially with my wpforo setup that sounds similar but fixed it quickly because I had experienced a HUGE problem on an unrelated WIKI site which was not using wpforo.

It was to do with the slug - in my wpforo case 'community' (blog) and overlapping with the forum root being deciphered and hitting 'community' slug confused the app. I solved it by changing the "community" slug on my secondary (non-wpforo) page to something else while retaining the front-end - Name menus etc appearances, something like "community-xyz" might work - of course xyz could be anything -  or as in my case I changed 'community' out of that original non-wpforo slug altogether but it still appears as "Community" in all other front end aspects.
Sorry if this is a dead-end, I didn't pay much attention to what else  may have done to resolve it when I ran into it with wpforo because after an hour or so of perplexing tinkering I remembered the first issue and I think I did the same thing or similar to fix it. I've since changed this site so I can't help with any more than vague memory.

Just thought it was worth mentioning.