Dear Colleagues,
Thanks very much for your reactions. By now, I have found out what went wrong.
It has been said more than once at various places in this forum: most problems with printers
such as Epson's SC-P600 and the like, are due to user errors. I am embarrassed to say that
my problem is yet another illustration of this point.
What I did: I am used to feeding all my A3+ papers (Hahnemühle: Baryta, Pearl, Canson: Etching Rag, Baryta2, etc.)
into my SC-P600 printer by means of the Front Poster Board option. For all these papers, all of which are 0,3 mm thick or more,
this has always worked perfectly. For Awagami Unryu thin, which is 0,13 mm thick, it did not.
It led to the colour bleeding and smearing mentioned in my original post.
What I should have done (and ultimately did after all): I should not have used the Front Poster Board option
for feeding the Awagami Unryu thin paper into the printer. Instead, using the Front Fine Art option works perfectly well.
So "I made a learning", after all.
Sorry for wasting your time and thanks very much, once more,
for your feedback, much appreciated!
Best, Jan