Visualbyte's advice is good - a little extra weight can help pull the pen tip more tautly into line with the gondola. So I think this is probably as simple as the pen tip dragging a little behind the direction of movement. This is normal, and with a good taut "hang" and a firmly perpendicular pen, it can be reduced, maybe so much you'll not notice it, but it'll never really go away. As long as there's friction between the surface and the gondola.
The direction that the pen lift servo swings in from can also move the pen too, during the lift. If it is horizontal (so it swings in from the side), it can pull the pen at the same time as lifting, or dropping. Did the outer-most shape join up naturally, or is that a manual fix? It looks like there was an overlap.
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