(Continued)
If you translate x or y even fractionally away from [0,0] (say, [0,0.00001] then the mesh will reappear.
Now more fundamentally, the issue appears to be just the spline mesh and there is no relation to the spline itself. The construction diagram can be reduced to just the Add Spline Mesh Component, and Set Start and End. Set the Start Pos at [0,0,0], Start Tangent [0,0,0], End Pos [0,0,100], and End Tangent [0,0,0]. Again the mesh will disappear. For more reasonable tangents, you can use [0,0,10], and [0,0,10], but again no change. If one of the tangents is set to a non-aligned axis, say [0,1,10], then again the mesh will appear.
