I am having the same problem. I have the HP T830 plotter, and what little research into this issue I have done seems to suggest it could be a printer driver, but a new driver did not solve the problem.
However, I have had some success getting inserted PDF's to fully print by creating a PDF using Chief's save as PDF feature, then opening the PDF in acrobat or whatever PDF software you use, open the print dialog, choose your printer, click on the "advanced" tab, select "print as image".
If I come up with anything else that works I will post it here.