Problem on polyline-polyline fillet when fillet ends or starts in polyline control point

I have problems filleting two polylines if fillet lands on polyline control point.
On image there is a red fillet, which i am not able to generate. If changesing radius smaller or larger there is no problem.

Here is a file problematic_polylines.3dm (207.2 KB), where i am not able to fillet with radius 8

I am running Rhino 5. SR12

Making a fillet that ‘eats’ its entire base geometry (be it curves or surfaces) is always problematic, yes.
You can manually work around this by using the Arc - Tangent command. Pick the vertical-ish line on the left as your first tangent curve and then type in the radius 8. Snap to the other line and pick the inner arc.