Here is a video showing the problem.
Here is the code, attached to an Area2D. Godot3.0 on Ubuntu.
func _on_Area2DLeftAim_input_event( viewport, event, shape_idx ):
touchPOS = event.global_position
$aimingStick/support/target.position.y = touchPOS.y
print("Touching: ", str(touchPOS))
Can anyone offer any advice as to what's making it go wrong? Thanks so much...