Project Node results in Invalid BREP Despite Simple Input

I’m not sure what I’m missing here.
I’m using the “Project” Node.
Input Geometry is a simple box rectangle.
Input Plane is XY.
Output Geometry is invalid.

projecting a box on a plane basically flattens it. the reason it’s an invalid brep is that it has zero-length faces and edges.

just by looking at the box, you can tell that all four of the side faces will be reduced to 0, while the top and bottom faces should be alright. to check:

But is that what you’re after, a flattened box? I’m guessing not. If you explain what you’re trying to accomplish, maybe we can help