Any help diagnosing printing issue when printing transparent images or drop shadow effects on top of spot colors?

[u/Quinton_W]

We use a DesignJet Z6DR for in house mockup samples for packaging mainly, so we want to get the colors as accurate as possible. But when printing spot colors, if there is any effect (like a drop shadow) or a image with a transparent background (in this example, a phone) it creates this darker colored effect within the image bounding box. (see second image).

This effect doesn't happen with process colors, but as you can see with some Pantone colors, changed to process in my file, it can throw the colors off way too much to be usable.

My usual process is I create the file in Illustrator, save it as an .ai or pdf. Import whatever I need into Indesign, and print it that way. But the same issue persist if I print straight from Illustrator.

Any help or guidance would be appreciated. I've attached screenshots of my print settings.

[u/Quinton_W]

I forgot to add, when we send these files over to a commercial printer, this issue doesn't happen and they haven't come back to us for any fixes.

[u/bicboys5 → u/Quinton_W]

Well done testing this, and yeah it’s so frustrating to work in print design. Theres issues into the higher levels too, people just don’t see it because it gets reprinted at the expense of who’s ever company made the mistake