1.
I guess you tried all ? the different pc3 printer you have, you played with quality and so on ?
Any transparency on the objects or layers ?
just in case : put a bright color and change again the color by putting it more white if you want to avoid the use of transparency.
2.
In an other hand, can you try the SOLID command (not the Solid hatch) on your drawing to see if it does the same effects ?
(it is a 3 or 4 vertex object only, you ll have to put several of them sometimes)
Hope someone will help better than me. You pdf is nice and deserves unicity, usually, I don't like them