It has stopped I'm guessing it was dropping to the Facebook ad at the bottom which is gone.
No it isn't that mate.
I've changed forums from general discussion forums to question and answer forums and a couple of other types like article setup and stuff. Then changed them back here and there. And the forum has just lost its marker of where post 2 starts which is different depending on which forum type you're in. So I've just started the forum process of rebuilding the threads and it'll take an hour or so to recount them and whatnot.
Problem is with doing this, peoples post counts can change dramatically as it will literally recount all post in all threads in all forums.
So let's see what happens later when it's complete...