The red and green polycurves are similar, except the red one has an additional segment on the end opposite the problem. As shown below, neither _Extend nor _ExtendDynamic can dynamically extend the red curve with Type=Smooth or Natural. (It will dynamically extend with Type=Line or Arc.)
+1. I’ll try to find an example for a surface but it was in the middle of my class so I couldn’t stop to write a bug report.
It made me look like a fool btw! I’ve been giving this course for ten years. First time on RH8 this year, and I find myself having to improvise a new method on the spot to finish the exercise.