[Gmsh] Problem with volume definition

[Alessandro Vicini]

In the attached Test_05.geo file (together with spline.geo and background.geo which are merged into it), I need to generate the Volume between the internal and external surfaces (which would be the difference between volumes 2 and 1, as defined in the file).
The problem is that, in the definition of the internal volume, gmsh sees its boundary surfaces as "embedded", as can be seen from the attached screen.jpg. This is maintained when the new volume is generated, so that the "hole" is not obtained.
Somebody could please suggest how to work this out? Thank you!

Alessandro
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