Extrusion calibration vs. default Vellemann slic3r settings

I am trying to print the Maker Fair Robot thingiverse.com/thing:331035 (in 65pc) and got the problem that the parts won´t move as the perimeters get too close to each other.

I wonder if this is caused by the default Vellemann print settings for slic3r from the printer´s manual (now using slic3r 1.2.6).

Print settings:
Default extrusion width: 100 %
First layer: 100 %
Perimeters: 170 %
Infill: 180 %

Filament settings:
Extrusion multiplier: 1.15

Printer settings:
Retraction Length: 5 mm
Extra length on restart: 0.1 mm

I have already read something about calibrating the extrusion length and if I did this correctly, it was way off. Though, all the other prints before came out fine. Of course, those didn´t have such fine structures like the robot has.

Are you using the default values, especially for “Extrusion multiplier” and “Extrusion Perimeters”?
Is “Extra length on restart” really necessary?

Lars