I’ve noticed splitting one mesh with another sometimes returns invalid pieces. For example, try splitting the smaller mesh with the larger one in this Rhino file. (I’m using Mesh.Split(IEnumerable(Mesh), or MeshSplit at the command line.) The method returns 2 meshes, as one would expect, but both are invalid (no vertices).
Any advice on a fix? Interestingly, the method succeeds if the file units are changed from inches to meters and the model is scaled accordingly. (But not if the doc tolerance is increased by 40x). Hoping for a general solution.