[Gmsh] Cannot mesh a simple volume

[Fabrice Pepin]

Hello,
I try to mesh a simple box volume using version 2.16 without success and I do not understand why.Everything is fine up to 2D mesh. I want to have 4 hexa "piled" together.Picture 1 shows quadrangles (with shrink factor) which are OK for me.On the GUI, I click on mesh 3D and then the quadrangles are split and 3D mesh gets error (picture 2). 
Can anybody tell me what I am doing wrong ? Thank you in advance.Fabrice.

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