I learned that it can be very difficult to find the center of an arc segment in a Polyline.
The Autosnap has understandable problems but I can't see why I have to search so long with the "Center SC" snap in a blanc area to find - by accident - the center.
Would it be possible and maybe also in my understanding more logical to find the center with just a mouse-over / selecting the Polyline arc segment like the normal arc line?
Here a Test dxf - try to find the center of the biggest Polyline arc segment. The small arcs are easy ...