What causes this ghosting? I can't seem to figure it out. In the middle of the opening you see there is a generated support structure auto added by Simplify3d.
Using version 4.0.0
Is the pitch of those variations equal to the pitch of the belt/gear driving the axis? I think if there are slight variations in radius, the head will speed up / slow down ever so slightly during the move, leading to periodic tiny over/under extrusion.
I also see those kinds of patterns on my CNC mill, matched to the ballscrew pitch. In that case it's because they aren't perfectly straight and is pushing the table back and forth in the bearings as they rotate. Depending on how the printer is constructed, that could also be a factor.