Blank page appears in exported quiz

I know in my 40 years or so of using Toolbook this has happened before but I can't seem to put my finger on the best way of solving it. Students take a randomized (selects 20 questions) quiz but at some point get an empty page without content or navigational devices that stops them cold. Frustrating for all concerned. I have used the usual validation tools in Toolbook but everything pops up fine. Do I just keep trying to re-export smaller sections of the book to see if I can narrow the one page down that may have an error in it?