Looks like the issue is they put a full youtube url in between the u2b tags. This works on the thread page for some reason, but when you click Go Advanced, it renders the thread on that page as well, only it doesn't do the youtube embed properly. It tries to load:
And instead of the video in the iframe, it loads a 404 page. There must be some kind of redirect logic on youtube's site somewhere that then causes the entire page to go to the youtube homepage (most likely they have the redirect when the referrer isn't what they expect).