Inconsistent extrusion depending on startpoint

[Kaibob]

I'm seeing an issue when printing more complicated objects like in the pictures below. I tried almost every combination of retract, startpoint, coast, wipe, speed, temperature and so on. The printer is really well calibrated and sqaures or circles come out perfect. Also objects like Moai http://www.thingiverse.com/thing:149271 or Gecko http://www.thingiverse.com/thing:1363148 come out with a very smooth surface.
Like you can see in pictures the diagonal front is perfect too. On the backside there are stripes which align with the holes. The object is printed with fixed startpoints on the left back. The area between the holes is fine, but when the layerheight reaches the first hole the path goes "inside" the object and when it comes back to the surface the extrusion is a litlle lower than at heights where there is no hole. It is a little hard to describe, but maybe somenone can give me a hint how to get rid of this. This is the last thing i just can't get fixed, i'm fidlling around with this problem for months now and asking here seems like my last resort.

Sliced with S3D
Printed with PLA at (calibrated) 210°C
Bed 50°C
60mm/s inner perimeter
24mm/s outer perimeter
2 Outline shells
0,2mm layer height
0,4mm nozzle

[CompoundCarl]

That looks like ringing to me. It's really common around holes like that, since the printer is making small quick changes that sometimes create vibrations for the rest of the line along the surface. Might want to try reducing the speed by 50% to see if it still happens at a lower speed (if it goes away, then that would prove it may be vibrations)

[Kaibob]

Hmm, rather not, ringing, caused by high accelerated speed change would, in my eyes, look like this.


But i'm always open to try, so I reduced both perimeter speeds to 30mm/s but it changed nothing. It still looks like, if the toolhead comes back from the hole to the surface as if it would underextrude