Hi, How is the image quality otherwise? My first guess is the print head is too close to the paper. This could look like the ink is blotchy or uneven. If the print head is too close, there could be some contact with a corner of the print head carriage which would leave an unexpected stain on the print side of your paper. I would reach out to Canon or Hahnemuhle to see if they have a recommended print settings for that paper. Shades of Paper, a supplier of both Hahnemuhle and Canon has been a really valuable resource for this type of troubleshooting for me. I use a similar canvas and my setting is;
Media Type > Fine Art Papers > Canon Artistic Matte Canvas
The ink on the platen and in the ink suction holes is normal but does require cleaning every so often. This comes from borderless printing. That ink would generally get on the back of your prints. It can be a pest if you're stacking your prints together and don't realize. Since it's a thicker pool of ink it doesn't dry as fast as the thin layer of printed ink. This will result in your stack of prints having random smudges of ink which is inadvertently transferred from the back of the paper that was on top.
