PlanarFigure interaction mechanism prevents control points of a PlanarFigure to be placed on top of each other. This works fine in the current version for ROIs and other structures with undefined number of control points. However, for lines, crosses and other figures with a fixed number of control points, the last point can be placed on top of another point; the corresponding check does not work properly.
The cause for this is that not all previous control points have are considered when checking for point overlap.