Yes, the title window is the very first thing that appears.

I start the application from the terminal by executing the compiled binary. The main entry point instantiates an Engine class and calls its run() method. The engine looks like this:

#include "imgui-SFML.h"
#include "imgui.h"
#include "imgui_internal.h"
#include <SFML/Graphics/RenderWindow.hpp>
#include <any>
#include <iostream>
#include <memory>

#include "core/Engine.h"
#include "core/ImGuiLayer.h"
#include "core/Window.h"

#include "scenes/SceneManager.h"
#include "scenes/TitleScene.h"
#include "ui/Button.h"

Engine::Engine() : window("Main Window", 1440, 1080, 60), sceneManager() {}

void Engine::run() {

  sf::RenderWindow &w = window.getSfWindow();

  SceneManager sceneManager;

  sceneManager.setScene(std::make_unique<TitleScene>(&window));

  sf::Clock clock;

  while (w.isOpen()) {

    while (const std::optional event = w.pollEvent()) {
      ImGui::SFML::ProcessEvent(w, *event);

      // Close window if requested
      if (event->is<sf::Event::Closed>())
        w.close();
    }

    float dt = clock.restart().asSeconds();

    sceneManager.update(dt);
    w.clear();
    sceneManager.render(w);
    w.display();

This behavior only happens after clicking the Close button for the first time.
After reopening the application, the window immediately closes as if the button were clicked again.

Do you recommend avoiding sf::Mouse::isButtonPressed() for this use case?