The first link "/Toolbox/Subpage Demo" is broken.
I wonder how this can happen. I thought, these pages are generated somewhat automatically?!?
I'm not exactly sure what's happening - I'll continue to investigate just so that I can tidy up. It's fairly clear why the problem started. It seems that in March last year, while we were investigating extra tools, I accidentally created a page with a double '/' in the URL - that's why it starts with '/' in the link, where it shouldn't. If you load that page by typing in the name with a double '//' it actually loads the correct page. I suspect that I redirected without leaving a '#REDIRECT' on the page, making it invisible, yet showing up if you search all namespaces. I don't know whether that can be tidied or not. I'll see if I can find out more.