Cannot print any images to PDF

https://security.duke.edu/policies/minimum-security-standards-servers

We have two links at the bottom: print and pdf

Printing works fine.

PDF uses the print stylesheet, but doesn't print any of the checkmarks from the table.

We tried using all of the available PDF libraries. Currently using dompdf.

Dompdf has CSS compatibility with the code we used for styling the images: https://github.com/dompdf/dompdf/wiki/CSSCompatibility