Scene not properly loaded when switching back and forth

Question

Problem
The Unity project I build is targeting iOS, Android and Windows X64. I have two scenes, A and B, whereas A is the main menu scene of my game and scene B is kind of a level selection scene in which the user can choose a level to play. From scene A I can navigate to scene B and back again. When running the game in the Unity Editor, everything behaves as expected. The problem arises, when I run the game on the target platforms (real devices). Then, when navigating like A --> B --> A, I end up in scene A being rendered as a black screen, except the FPSIndicator game object which is still rendered and doing its job. The FPSIndicator game object is a small piece of code which draws itself to the scene in the OnGUI callback. Nothing else is displayed.

Setup of Scene A
I have a Unity UI button there ("Drag and Drop"), which, when clicked, loads scene B using this code:

using System.Collections;
using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.EventSystems;

public class GameTypeButtonController : MonoBehaviour, IPointerClickHandler
{
    public ButtonSounds ButtonSounds;
    public string SceneNameToLoad;
    public GameType GameType;

    public void OnPointerClick(PointerEventData eventData)
    {
        StartCoroutine(Do());
    }

    private IEnumerator Do()
    {
        var animator = gameObject.GetComponent();

        if (animator != null)
        {
            animator.SetTrigger("Clicked");
        }

        var audioSource = gameObject.GetComponent();

        if (audioSource != null)
        {
            var clip = GetRandomAudioClip(ButtonSounds);
            audioSource.clip = clip;
            audioSource.Play();
            yield return new WaitWhile(() => audioSource.isPlaying);
        }

        Logger.LogInfo("[GameTypeButtonController.Do] Setting game type " + GameType);
        GameManager.Instance.CurrentGameType = GameType;
        SceneManager.LoadScene(SceneNameToLoad);
    }

    private AudioClip GetRandomAudioClip(ButtonSounds buttonSounds)
    {
        var numberOfAudioClips = buttonSounds.AudioClips.Length;
        var randomIndex = Random.Range(0, numberOfAudioClips);
        return buttonSounds.AudioClips[randomIndex];
    }
}

The scene looks like this:

Setup of Scene B
In scene B, I have a button in the lower left which brings me back to scene A when clicked. This is not a Unity UI button, but a regular sprite with a CircleCollider2D attached. The script on that button looks like this:

using System.Collections;
using UnityEngine;
using UnityEngine.SceneManagement;

public class HomeButtonController : MonoBehaviour
{
    public ButtonSounds ButtonSounds;
    public string SceneNameToLoad;

    void OnMouseDown()
    {
        StartCoroutine(Do());
    }

    private IEnumerator Do()
    {
        var animator = gameObject.GetComponent();

        if (animator != null)
        {
            animator.SetTrigger("Clicked");
        }

        var audioSource = gameObject.GetComponent();

        if (audioSource != null)
        {
            var clip = GetRandomAudioClip(ButtonSounds);
            audioSource.clip = clip;
            audioSource.Play();
            yield return new WaitWhile(() => audioSource.isPlaying);
        }

        SceneManager.LoadScene(SceneNameToLoad);
    }

    private AudioClip GetRandomAudioClip(ButtonSounds buttonSounds)
    {
        var numberOfAudioClips = buttonSounds.AudioClips.Length;
        var randomIndex = UnityEngine.Random.Range(0, numberOfAudioClips);
        return buttonSounds.AudioClips[randomIndex];
    }
}

The scene looks like this:

General Notes
Two objects use DontDestroyOnLoad: GameManager and MusicPlayer.

What I have checked so far

Scenes are properly referenced in Build Settings
As I use Unity Cloud Build, I have disabled the Library Caching feature to avoid issues with old build artifacts (so every time I build, I do a proper, clean build)
I can locally build all three platforms (Unity reports it as "Build successful"). So no build errors.
I am using LoadSceneMode.Single (default)
I am using the same Unity version locally and in Unity Cloud Build: 2018.3.0f2

Update 2019-02-19:
When I navigate from a third scene C back to scene A using the same mechanism (a sprite button calling a coroutine), I also end up on the very same black screen. So the issue probably exists within scene A?

Update 2 from 2019-02-19:
Here's my GameManager code:

using System;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using UnityEngine;

public class GameManager : MonoBehaviour
{
    public EventHandler LevelStarted;
    public EventHandler LevelFinished;

    // General 
    public GameType CurrentGameType;
    public GameScene CurrentScene;
    public int CurrentLevel;
    public static GameManager Instance;
    public GameLanguage Language;
    public bool IsMusicEnabled;
    private string gameStateFile;

    void Start()
    {
        if (Instance == null)
        {
            gameStateFile = Application.persistentDataPath + "/gamestate.dat";
            Load(gameStateFile);
            DontDestroyOnLoad(gameObject);
            Instance = this;
        }
        else if (Instance != this)
        {
            Destroy(gameObject);
        }
    }

    public void Save()
    {
        Logger.LogInfo("[GameManager.Save] Saving game state to " + gameStateFile);
        var bf = new BinaryFormatter();
        var file = File.Create(gameStateFile);

        var gameState = new GameState();
        gameState.Language = Language;
        gameState.IsMusicEnabled = IsMusicEnabled;

        bf.Serialize(file, gameState);
        file.Close();
        Logger.LogInfo("[GameManager.Save] Successfully saved game state");
    }

    public void Load(string gameStateFile)
    {
        Logger.LogInfo("[GameManager.Load] Loading game state from " + gameStateFile);
        if (File.Exists(gameStateFile))
        {
            var bf = new BinaryFormatter();
            var file = File.Open(gameStateFile, FileMode.Open);
            var gameState = (GameState)bf.Deserialize(file);
            file.Close();
            Language = gameState.Language;
            IsMusicEnabled = gameState.IsMusicEnabled;
        }
        Logger.LogInfo("[GameManager.Load] Successfully loaded game state");
    }

    [Serializable]
    class GameState {
        public GameLanguage Language;
        public bool IsMusicEnabled;
    }
}

Thanks for any hints!

Scene not properly loaded when switching back and forth

Answers (1)

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