Surface Blending - Unexpected pinching

 From:  PaQ
Hello everyone, sorry to bugging you with some questions again :o)

I was trying to do a multiple fillet radius by hand, and I came on some strange result with the surface blending function.
So here we go :

So I start to create 3 circle, (I did a mirror of the first one), and I sweep them along the top object curve. Then I did
a substract booelan.

I remove the unwanted surface

And finaly I blend the two surface with G1 continuity

As you can see there is a strange pinch in the blending.

To compare here's the same object using G1 on G1 surface blending.

So I suppose there is something wrong in the blending fonction :S
I have attached the .3dm file so you can play with ... Of course in this exemple I can just trim the object in half, and only keep the working side :P ...
but I don't like the idea ^^

EDITED: 4 Dec 2015 by PAQ