What printer do you use. This is a mechanical issue. It's something binding as the one x or y is traveling could be a bearing or the stepper motor it self. It prevents the arc from being fully formed even though the machine thinks it is key point you made is that randomized z seam leaves the same mess, but if notice it's not all the layers are cut short only some.
Take the belt off and move the axis by hand slow and easy do you feel anything that isn't smooth like silk? That would be it. Feel the stepper is the drive gear tight any slip ?? Any play in the shaft side?
Edit
Looking at the pictures again I'd bet that if you went taller and printed faster, it would be even worse because the bad part got hotter and more bound up more Alternatively printing faster might make it better because you have the inertia to push past the binding spot.