There are fragmented join geometries when drawing the joints between line segments that create very sharp angles. The fragments are presented by wrongly drawn long ray that start from the join.

This work this around, you can set the DefaultLineVisualGeometrySelector property of the LineSeries3D.

lineSeries.DefaultLineVisualGeometrySelector = new Telerik.Windows.Controls.ChartView.Geometry3DSelector();

Note that his workaround works because it removes the joints between the line segments. This prevents the origin of the problem, but it makes the line more jaggy.