Creating vertices and faces with marching cubes lewiner

Hi there,

I have a question regarding the use of the marching cubes lewiner algorithm. I use this function to create faces and vertices out of a binary image. When I calculate the area of each face, some faces have an area of 0. In these faces two of the three vertices overlap, so it makes sense that the area is 0, as it is a line. My question is: Why does this algorithm give faces with an area of 0?

When I use the option: allow_degenerate=False, some of these faces are removed, but not all of them. Why is this?

Thanks in advance!