I often have to prepare materials for reprints, and our book files are set up as multiple chapter INDDs within an INDB.

Starting with Version 20.0, opening an INDB from a previous version of InDesign maintains the correct pagination in the Book window, but opening the INDD files through the INDB shows the page numbers have reset their numbering to 1 with each chapter. Preflight does not flag this issue, and the numbers are not recalculated by default in preparation for exporting. Instead, Update All Numbers must be manually run on the book, after which the counts are again correct. This means also having to manually sit there and hit save on every indd as it updates as well - annoying as some of our books have over 60 chapters.