It sometimes happens that your B-Rep or mesh model contains inverted faces, i.e., the faces whose normal vectors are pointing in a wrong direction with respect to the bounded material. We have devoted a couple of blog posts to that issue already (see here and here), but so far it was not straightforward to see if your geometry suffers from such sort of defects or not. In the next version of Analysis Situs, the inverted faces & facets will get your attention right out of the box: we now render all such problematic entities in red color.
Analysis Situs keeps going to give you an open CAD platform for prototyping engineering software without any bit of commercial code inside. Stay tuned.