Epson L1800 magenta dust beside black at right area of A3 paper

[Ink stained Fingers]

Is there a possibility to fine tune the platen gap?

I'm not aware of another way to change the platen gap in the L1800 besides this 'thick paper' option. You find specific adjustment options in higher end printers for the paper thickness . Isn't it o.k. with the L1800 now ?