If you create a page with a very long name, the page shows up as existing in some places, not existing in others, and it is unaccessable anywhere. If it was created as a child, or a page exists which links to it, it is impossible to rename it to a shorter name without directly editing the database, because the only way to rename pages which are not orphans is by viewing the page and clicking 'Rename Page'. I believe the problem is the 256 character limit for URLs, which long-titled pages can easily break.

Suggestions for a solution would be:

1. Limit page title length
2. Provide a place where you can rename unorphaned pages from the Content page (similar to how Orphaned Pages can be renamed).