Mhh interesting ... I have a similar issue.
Have you checkt die filament diameter?
How is your role of filament guided? Is it hard to turn it?
What about the temperature of your extruder (did the change in current do anything?)? is it getting very hot?
How is your bowden tube guided? is it twisted (and maybe therefore the filament causing inconsistent extrusion)?
How is your part cooling? Maybe you are cooling the heatblock and therefore the extruder having troubles extruding a constant amount of filament?
Have you tried playing with the acceleration of the Extruder?
The strang thing is, that I ran into this issue just recently. but it looks exactly the same ... in the most part I have constant extrusion but then a bit under and a bit overextrusion causing the walls not being consistant.
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