The first edge "JoinCurve013005001" is not good.

It is mathematically valid, but it is wrong for BlendCurve algorithm.

It is a BSpline Curve of degree 3.

It has 4 control points P.

But P1=P2 and P3=P4
On the other hand, you can see that the other curve is good, all control points are distinct:
So the blendcurve fails, because it doesn't support this kind of degenerated curves.