I had such good luck with my question the other day, I thought I might push that luck with the "big one".
With Epson's smaller K3 printers, the ones that have the pinwheels and also the rubber wheels that push (or drag) the paper through the machine, under the right circumstances an effect I refer to as "skid marks" or "railroad tracks" (same thing) occurs. I am referring to the SP 3800/3880 and their smaller thirteen inch brethren.
These marks might be described as 'chatter' lines, as if the paper were perhaps slipping and then being recaptured. The lines run perpendicular to the paper path, seem to occur right where those rubber rollers touch the material. Lines are about 2mm (roughly) apart and generally run along half the length of the print.
They occur in from one to several groups across the print, but never where all the rubber rollers are, just some.
They also look as though ink were getting pushed in front and then left behind and then picked up yet again.
Also, this problem appears to be humidity related. People who live in humid climates report it a lot. Here in Arizona, I see it seldom enough that I can't get sufficient repetition to really study it.
This is occurring with a smooth surface material.
I have devised some techniques that seem to provide improvement, but no cure.
Things that I know are definitely NOT the cause:
the pinwheels (front feed is used)
slow ink drying
dirty rollers
failure to swing a dead cat at midnight