Kitchen aid pasta roller getting oil on my pasta
I've almost never seen a pasta roller that doesn't do this at least a little. My 30-year-old hand-cranked one does it, same as my Kitchen Aid. I have always figured it was a side-effect of the plain bearings (essentially one piece of lubricated metal rubbing flat against another), which eventually blackens any oil intended to lubricate them.

I've been left trying to avoid the pasta reaching the edge as this is when it happens (as you've seen). When it does get discolored, my solution has always been to just trim off or discard the edge wherever it gets the black stuff on it.

I don't think you should be using the edge of the pasta roller to square up your dough in any case. If you want to make it more square, run the dough ball through, then fold the resulting sheet in thirds or whatever will make it narrow enough to feed through perpendicular to your first feeding and then run it through again. If you fold it carefully and feed it squarely, your edges will be quite square to each other. I think there may even be an illustration of this in the instructions for the Kitchen Aid pasta roller. It takes practice but it works well.