Drawing changes after saving!

I have just re-opened a saved drawing and the bottom edge of a closed polyline has an arc, when before saving it was straight. See image below, it is the bottom edge of the white polyline. I drew a rectangle, then 'rounded' the corners. Any ideas what has happened?

Please file a bug with a testcase dxf, or detailed steps of reproducing this bug.

our sourceforge bug tracker: http://sourceforge.net/p/librecad/bugs/?source=navbar