Under Rhino5 SR9, I’m getting some intermittent failures when using the Rhino.PlaneCurveIntersection to intersect a series of sections that were all cut from the same surface. In the example file, executing PlaneCurveIntersection under Rhinoscript fails to find an intersection on the red curve (at X=40), but it finds one on the black curve (at X=42). Under python, the command finds the intersection in both curves. There was a similar issue and bug fix for SR6 mentioned on the forum about a year ago ([Plane Curve Intersection Fails]). Could this be a related issue? I assume there’s no problem with the curves since the python version was working.