If I understand correctly, you're having the same problem we've always had. For example, a CHAPTER always starts with a recto, and if something within the CHAPTER such as a foldout image needs a recto page when the preceding text ends in the middle of a recto, then a 'blank' verso is generated. However, if the last page of the CHAPTER ends on a recto, and it's the last CHAPTER of the book, there will be no automatically generated 'blank' verso. Any CHAPTER other than the last will generate such a verso, if needed, but not the last CHAPTER.
We "solved" this by adding a 'dummy.page' pageset, which had a single recto page containing "Remove This Page" in large, blue font. It can be called by the occur=last CHAPTER <e-i-c> in a placement=after <usetext>, which will then trigger the automatic verso. Down side is, you have to edit the resulting PDF to remove that page.
Only solution we ever found that would work in PE.