Ah yes, it appears to be a Grasshopper 0.9 - 1.0 compatibility issue… somehow it escaped my notice that the mac version of the component had an extra ‘N’ output parameter. 
I had mistakenly assumed that the .gh files produced by Mac Rhino 5 and Windows Rhino 5 would be cross-platform (our organization won’t be upgrading to Rhino 6 licenses any time soon)
Is there a complete list of such components that have been deprecated between versions 0.9 and 1.0? As it stands, a file with a GH1.0 ‘Brep CP’ component completely breaks the definition for someone opening it in GH0.9, leaving no trace of where the component or its wires were connected.