Problem with Mesh Swept

There is something I don't get right with the Mesh Swept option.

I used the model "biased_resonator_3d_modes.mph" from the Model Library as a starting point. There they built a mesh on one face of the structure (figure 04) and used the Swept option to mesh all domains by repeating the initial 2D mesh (figure 05).

I tried the same thing (figures 00, 01, 02) but I'm continiously getting an error message (figure 03) when running Swept. The cross section of my structure is constant along the model, so there should be no mismatch issues.

What am I doing wrong? What are the requirements to build a mesh out of a 2D mesh?

Thanks!