Mark this is what I see.
I'm not alone (also in this forum) to notice these imperfections, that yes, maybe are difficult to see but there are ! Even Epson tech support told me about the existence of these unfamous marks !
Now, I tried many combinations for the platen gap, paper thickness, paper feed adjustment, drying time and color density but nothing.
If my machine is not "a normally functioning P800 printer", frankly I don't think that if I call back tech support they want to talk with me about it !
Anyway, I'm printing with my new P800 right now and trying also bigger sheet (until A2) to see what happens. The curios thing is that maybe the issue only arise with the Canson papers (?). Maybe is worthy to try Hanemuhle Baryta and/or Espon Baryta and for sure I will !
"under a strong enough magnifier"
It's enough a strong light to see it !
Best regards
G.