I just encountered the weirdest bug ever.
Let's say I have a page with the slug "page1". On my static home page, I have a link pointing to "/page1/". All was working fine until somehow the slug for that page was changed to "abc-page1".
When I clicked the link on the home page, which still pointed to "/page1/", I was brought to a mysterious page that rendered all the pages in the database overlaying each other, creating an ugly mash of text. When I renamed page1's slug back to "page1", all was working fine again.
Weirdest problem ever, huh?