Well, pens *are* hardware. The two eyes don’t look different (to me) in the original file, so there’s something going on with the hardware that is causing that difference. It could be the detailed shape of the egg, the angle of the pen, the dryness of the pen tip, the angle of the pen tip (sharpie tips do tend do deform over use), or so forth.
There are ways to narrow down exactly what the issue is. For example, if you reverse the path on the fill, so that it goes the other direction, will the “dark” eye move? Will a small change in the pen arm centering have an effect? Does being more careful with pen centering and height make a difference?
