Update SplineMesh in realtime

[Polosatiy]

Hey guys, Im trying to update my spline mesh in realtime, by adding/removing points on that, and as a result updating the mesh, but some why it doesnot work properly in realtime, while works ok if I do that manually in edit mode.

In editor, updating is being done in construction event. In play mode I just add a new point in BeginPlay, and it behaves strangely.

Here is my blueprints, and in the end what it builds up.

Can you advice me what is wrong?

Thanks.