Bleeds missing from IMDB file

Ok 2nd quandary of the day: when I export to print PDF from my IMDB book file, I can't get bleeds to work - the content just extends to the crop marks. Bleeds work fine when I export from the individual INDD files. I've tried exporting from the book file with "use document bleed settings" checked on and off and tried directly editing the book's document setup, but nothing seems to work. What am I missing? Is it because some of the INDD files in the book have bleed on and some don't?