We used to get this while printing orange on our old Edge and my coworker mentioned that it was a "cat scratch". I don't know all the details, but it has to do with the temperature. In our case it was running too hot. I did find this comment in another article though "Also, if you're doing backing white, you may need to turn up your print temp in the software. Usually, overprint compensates enough, but turning it on manually in the GSPplot screen is always a good safeguard."
Try adjusting your temp manually and see if that helps. Good luck!