I have experienced the following a couple of times now:
I have a survey figure with curves that I have edited to prevent crossing breaklines. The next time I open the drawing and database the figure has changed itself from the way I left it. It appears that C3D wants to force the arcs in my figures to be tangent, even if I did not define them that way. Sometimes I will break an arc on a point-on-curve so I will get two curves that share the elevation at said point-on-curve. Upon re-opening the drawing I get and s-shaped reverse curve as seen in the attached picture. Does anyone else have this problem or am I just trying to do things with figures I shouldn't?
(Using C3D 2010 update 3.1)
(running C3D 2012 sp3, Win7 64bit)