The script was successfully running, but after a while it looked like this, and I couldn't keep doing the same process of adding new nodes (Element.faces) each time it ran, so the Dynamo player displayed an error.
Any solutions ?
This looks more like a Dynamo issue than a pure Revit API question. I have no idea myself, just looking at the image of the nodes. Maybe the folks in the Dynamo forum will know what the problem is right out of the box:
Jeremy Tammik 
Developer Advocacy and Support + The Building Coder + Autodesk Developer Network + ADN Open
Developer Advocacy and Support + The Building Coder + Autodesk Developer Network + ADN Open
