Issue: Book - Can't delete book chapter

I created a book earlier today, I added new chapters by selecting existing articles, but found that using this method made it hard to create sub-chapters in books (another issue is sub chapter of sub chapters don't show up in the list).
I change some things about, and needed to delete some chapters from the book. I went through the delete procedure (on the edit page), selected the correct chapters to delete, and pressed delete, only to find out they were still there.