Digital BW, The Print

I have a 2400 printer which gives perfect nozzle checks and yet it
produces faint microbanding throughout the print.  The banding is in
the direction of head travel and appears visible to the naked eye on
Best Photo setting and is visible with a loupe on the Photo RPM
settings.  High speed is unchecked.  I've contacted Epson service and
they've requested that I test the problem using Epson paper (problem
still exists).

Does anyone have any thoughts on what it might be?

Ed