Grazie 1.000 for your help. In the meantime is there a way to modify the file using notepad or super difficult? The strange thing is that I tryed again the "double passage" and it worked... strange...

<t>Ciao guys I got same problem. I use "Autodesk Tinkercad" (tinkrcad.com) to create some objects then I export them as OBJ+MTL. No way to import this file in SH3D. I found a workaround (very complicated). sometimes working sometimes not. I import the OBJ in "3D Builder", free Microsoft App, I ...