Simple surface intersections fail (Rhino 5 Win)

In the attached model file there’s a set of 2 triangular surfaces and its mirror. When I intersect either set, I get either a one segment curve or “no intersection”. Both results are incorrect. Also, which set has an intersection seems to change when I restart Rhino!

It seems strange for such simple intersections to be buggy. Any ideas?

I apologize in advance if this isn’t the right forum.

intersect_bug.3dm (40.0 KB)

I see - yeah I guess it is odd that you only get the triangle if you extrude the the faces in opposite directions and intersect the solids - I suppose this is because the surfaces are coincident rather than fully intersecting and the solids at least provide faces that are not coincident. @GregArden, is that what’s going on here, only edges really count in this situation, with two partially coincident faces?


As an addendum, the same problem exists with meshes and MeshIntersect. Thx., -arman