Opening window node makes me lose 10fps

Godot Version

4.0-4.3

Question

Opening window node makes me lose 10fps.
Empty project with just Godot sprite in it will run 60fps no problem. Once I add code below I will lose 10fps and the game will become laggy (Main project). How can I bypass this?

const WINDOWPRO: PackedScene = preload("res://lol.tscn")
func _ready():
  var _scene = WINDOWPRO.instantiate()
  get_window().add_child.(_scene)

Is the scene you are loading using the same script as the scene you are loading, which is using the same script as the scene you are loading…using the same script as the scene you are loading?