I tried that but it didn't change anything. But now i sorted something else out. If I try to print the Affinity PDF, it gets printed 4 times instead of just 1. I thought this was a different kind of problem, but it's not happening with other PDFs, so maybe the CMYK Channels get divided and somehow printed seperately?
All prints have the dark but not black hue I explained, but some (of these 4) are just a little tiny bit darker than others, but still not a opaque black Color
Maybe this gives further detail about the Problem, or maybe you found the problem somewhere else in my process