Got it to work!
Ok, after a few hours of pulling my hair out with a test site here is what I found…
1… With my main site, it had the previously mentioned problems with the BuddyBoss Boss theme. However, if I switched to any other theme there was no problems which let me to believe it was the Boss theme.
2… With the new test site I had only the boss theme, buddypress and SimplePress. In this case it worked just fine. Which then led me to believe that there is a plugin that caused a problem only in the case of = “Unknown plugin” + “BuddyBoss theme” + “Simple:Press”. – Began removing most of my plugins one by one. But nothing changed, same problem.
3… Began trying different settings within Simple:Press. FINALLY, tried the setting of “Integration – Theme Display Options – Limit forum display to within WP loop” and everything fine. 
So now that I have finally found a solution, my question is: “Is using this setting ok? Without any side effects?”