In a printing workflow, experienced user...
Created art in InDesign, exported print PDF (cmyk),
stepped 4 up in Quite Imposing,
Converted to black in Acrobat (conv' to emb profile)
full page graphic that was 4 up in first version lost 3 of them!
Summary: Was okay in cmyk original file
3 out of 4 disappeared (on same sheet) after converting.
I have files available, maybe some expert can have a look (J. Bessant looked at an earlier one before, is he still on here?)