I'm not sure how many people are going to have run into this. I've got an author site that uses WP-Types to create a simple one-to-many relationship with page tabs and review tabs. I have discovered that if URL Monitoring is turned on, saving a "books" post type causes an auto-redirection to save, which points at the latest "review" post in the book. The primary URL then auto-301s into a sub-url, causing absolute havoc on SEO if it's not caught in time.
You can see the layout of the page here:
If you need a dump of the theme or post types, I can get it to you privately; provided you aren't able to replicate the problem.
Note - I haven't checked this in Post 2 Posts but it's probably worth a look.