G4P - Each window is displayed for a moment on the display

Processing Libraries
1 
import g4p_controls.*;

public void setup(){
  size(480, 320, JAVA2D);

  createGUI();   // Each window is displayed for a moment on the display.
                 // I want this to happen in the background.
  
  customGUI();   // The windows disappear but flash on the display beforehand.
}

public void draw(){
  background(230);
}

public void customGUI(){
  window1.setVisible(false);
  window2.setVisible(false);
  window3.setVisible(false);
}

This is a short code with 3 windows.
Check out the launch of my app in this video:
G4P load windows :crazy_face:

If you have any idea how windows can remain invisible, please help.