PDF has strange black outline at printers end?

Hi all

I am trying to send a PDF of a book to a printing company in Japan (clients choice!), and I am doing everything I would usually do, supplying with crop marks and bleed.

When they open the PDF it seems to have cropped many of the pages and put a black outline around it.

I insert a screen shot (note this is page 7.  Page 6 is NOT white, therefore it has removed the crop on the left side!)

Any advice gratefully received.  At my end, some of the pages do seem to have a black outline for some reason on my PDF but they fall outside of the crop marks.

Thanks!

S