Acceleration is set to 5000 mm/s and jerk is set to 20 mm/s. I understand what you are staying about every time the extruder slows down. But if you look at my last picture, on the far right, the vertical edge, right in the middle, it does not over extrude. Also the cubes with no top that i printed, the corners are perfect. When I print the cube with the top, the top 3 layers (because I but 3 top layers) have over extrudes in the corners.
I am using the Artillery Sidewinder X1. I think you might be right about the Z axis being dirty. I remember the printer was pretty pretty well and then all of a sudden it stated to look bad. What do you use to clean off the Z axis?
thanks.