PDF output not displaying graphics that are imported PDFs

The graphics are properly linked and displaying correctly in Framemaker (no gray boxes). This is the 15th version of this document and I haven't had issues with these graphics in previous versions. They were untouched in this version as well, but suddenly won't show in the output PDF this time. Other graphic file types (EPS, JPG, and PNG)  are showing correctly in the output PDF. 

There are no errors in the Distiller log file. Using the "Save to PDF" option produces the same result. Re-importing the graphics also did not help.

Ideally I will be able to find a solution that does not involve changing the file type of the PDF graphics, as doing so would have a huge downstream impact. Any suggestions? Thanks