rgb or cmyk settings is the problem,
Photoshop or Illustrator are converting it for you when you inport it, posterprint rips as is. You may be able to select the colour in posterprint and set as a manual black
I get this sometimes. Can be something to do with the rip not recognizing the colours so replaces them with the ones in the rip. It comes up when the job is sent to print as colour not recognized.
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