Wavy sides, Repetier, original style Rostock

Puzzled newb here. Finally getting respectable prints out of a 2 week old Rostock.

I'm having trouble (or not... perhaps I'm being anal...) with the sides of straight prints. In this case, a 25mm cal cube.

I'm getting very consistent ripples -- for lack of a better word -- about 3 mm apart.

I've seen comments about changing some buffer setting, but that seems to be Marlin related, and this is running Repetier.

Any ideas? Aluminum rods, Traxxas joints...

-Ed