Skewness of Von mises distribution using two different methods

[A-ep93]

I want to use the circ_skewness code. Based on the code, there are two methods for calculating skewness:

Pewsey, Metrika, 2004
Statistical analysis of circular data, Fisher, p. 34

However, it seems the results are very different from each other. For instance, when I test for a Von Mises distribution (which should have a skewness of 0), the first method returns a skewness of zero while the second method returns a skewness of the order of thousands. What is causing this problem?

[A-ep93]

Here is an example of what I mean:
I generate a Von Mises distribution with mean 1 and kappa 10 with size 1000:
b=circ_vmrnd(1, 10, 1000);
I try to find its skewness:

[b b0]=circ_skewness(b)
Based on the code , b is the skewnss using Pewsey method and b0 is the skewness using Fisher method. These are the results:
b=0

b0= -65.78

Why do we have this difference?