Transparancy Map not printing to PDF

I’ve noticed recently that when printing to PDF, if a surface has a transparency map (to make a net), instead of being transparent like it shows in the rendered view port, it fills in with white.

Rendered Viewport the transparency map works fine:

Print to PDF using Rhino PDF and CutePDF the transparency is white instead. (shadows still work)

Is there a setting I’ve clicked by mistake or something that changed with a recent update?

Has anyone got ideas of what may be going wrong?