I realize that this thread is over two years old, but I am curious as to whether you have found a solution to your problem. I have the same problem and can find no resolution.
Epson technicians spent 8 days in my studio trying to solve the problem with no success. They then replaced my 9900 and the replacement printer has the same problem. It seems senseless to call Epson at this point.
I have adjusted the suction, the platen gap, have changed the tension on the auto roll back system, raised the humidity in the room from 28% to 40%, installed a voltage stabilizer, lowered and raised the amount of ink delivered to the paper, printed at different resolutions... and a number of other things that are not currently coming to mind.
This problem occurs on luster and semimatte paper, but not on matte.
Thank you in advance for any suggestions.
Warren