Yes, this appears to be a bug/regression; but there's a reason why it *does* manage to start ch 1 on a new page for some books and not others. It [currently/wrongly] depends on how much of the page has been filled, before deciding to start a new page for chapter 1. So if you want to force it to do so more reliably, there's an easy workaround:
Advanced Page, Other Tab (at the top), Open the 1st set of settings for "Page Layout and Spacing" and then change the "Page full factor" from 0.65 (default) to something like 0.30 and it will then start each book's ch 1 on a new page.