When building a Managed Metadata Navigation in SharePoint 2013, i noticed that some term driven pages were throwing a “page not found” error. I was able to resolve this, even if i don’t get the reason behind that feature.
When you build a navigation on a physical structure, make sure you do not have a toplevel term containing a friendly url with the same name as your subsite!
For example: mysharepoint.com/mysubsite/pages/default.aspx
A term “mysubsite” will be fine, as long as you don’t have any subterms. If you need subterms, rename your toplevel term to “mysite” or whatever and all subterms will be fine too. If you don’t rename your toplevel item, there will be a naming collision and links to pages will be broken.