New Chapters Added in the Middle of a Book
When you have a book that contains a sub-book that also contains chapters, any new chapter added to the outer book will be inserted before or after the sub-book in the table of contents, rather than as the last chapter. The "Manage Chapters" tool shows the new chapter in the correct location, and changes to the order via "Manage Chapters" are not applied as expected either.
This issue only occurs if a book contains a sub-book that also contains chapters. The problem here is that the outer-most book is incorrectly omitted from its own order-cache, which makes the parent unknown in the ordering function.
Fixed in the next release. Chapter orders will be automatically rebuilt by the upgrade script.