I have the exact same problem in UE 4.11.
This is driving me crazy: generating a spline via construction script, I can edit the spline in the editor (drag the spline points around) but the spline mesh doesn’t update to the changes. It really seems there are two splines, the one reacting the the construction script (add spline, add spline points, add spline mesh component, set start and end …) and the one with the spline points dragable in the editor.
By creating a public array and filling it with the refference to the splines created, it seems that each time the construction script fires, a new spline is created. The LAST element in the array always was “SplineComponent_338”, while the other elements were populated with “TRASH_SplineComponent_XYZ”.
When adding a spline point in the construction script and the blueprint actor was placed into the level, both the spline and the spline mesh had the same path, but when changing the spline by dragging it’s points around, the mesh did not follow. Even after recompiling the blueprint with the construction script, both had different paths.
Just to make sure: the construction script saw to destroying old spline mesh components and redrawing them. With a spline added with the “+ Add Component” button, the construction script worked fine.
I do not see this problem as resolved,
regards.