Digital BW, The Print

It could be the pizza wheels, although I've never heard of them
causing track marks on matte papers before. They can be easily
disabled by loosening the black clip that fix them in place inside the
printer all the way down on the left hand side. It's kind of hard to
explain without showing you a photo. The process is easily reversible. 

You will lose the ability to make borderless prints, or prints that
comes close to the bottom edge of the paper.

> I output a print for a client yesterday and found there were two
very sharp and fine, faint lines in the solid black areas of the matte
paper output from my Epson 2100 (spaced about 6.5 cm apart).