Dear Roy, Dear Lee,
I also cross-checked with AutoCAD 2008/2014 ... same strange "periodic" behaviour for a closed polyline
![smiley :-)](http://www.theswamp.org/Smileys/black/smiley.gif)
Indeed, strange, and I would even say, it is simply wrong ...
"Periodic" entities should repeat their values (points) after 1 period, think of a kind of spiral etc.
Many greetings !