Spline went rogue


Not sure why sometimes landscape spline starts to behave like unusual, and then I have to remove it and do a new one.
Like now, I can’t add more control points to it to continue it after I have reloaded the project.
As you see, I select the last point, then try to make a new point, but no segment is drawn and no new control point is made, you only see the pivot point there on the landscape without anything to it.
Is there anyway to fix this without removing and making a new spline again?