Loading screen coroutine stops executing for apparently no reason

Unity Engine
,
1

I’m making my first 2D topdown shooter game. I’m working on the loading part of the game. I have this functioning loading screen function (a method of my GameManager class) I made. I tried swapping between the main title scene and the first level a few times to test it. After loading the first level, then the title screen, when I try loading the first level back again the load screen is stuck.
The whole thing is working on a coroutine, and after some debugging I figured out the problem was that this coroutine stopped executing in a certain part of the code for some reason.

    public void LoadScene(int sceneIndex)
    {
        // If another scene is already loading, abort
        if (isLoadingScene)
        {
            Debug.LogWarning($"Attempting to load scene {sceneIndex} while another scene is already loading, aborting");
            return;
        }

        isLoadingScene = true;

        var sceneLoader = FindObjectOfType<SceneLoader>().gameObject;

        if (sceneLoader != null)
        {
            // Make the loading screen appear
            var animator = sceneLoader.GetComponent<Animator>();
            animator.SetTrigger("appear");

            // Make sure the SceneLoader object is maintained until the next scene
            // in order to not make the animation stop
            DontDestroyOnLoad(sceneLoader);
        }
        else // If a SceneLoader is not found in the current scene, throw an error
        {
            Debug.LogError($"SceneLoader could not be found in {SceneManager.GetActiveScene().name}");
        }

        // Unload active scene and load new one
        StartCoroutine(LoadScene_(sceneIndex, sceneLoader));
    }
   
    IEnumerator LoadScene_(int sceneIndex, GameObject sceneLoader)
    {
        float t = Time.time;

        // Start loading the new scene, but don't activate it yet
        AsyncOperation load = SceneManager.LoadSceneAsync(sceneIndex, LoadSceneMode.Additive);
        load.allowSceneActivation = false;

        // Wait until the loading is finished, but also give the loading screen enough
        // time to appear
        while (load.progress < 0.9f || Time.time <= (t + LoadingScreen_appearTime))
        {
            yield return null;
        }

        // Activate loaded screen
        load.allowSceneActivation = true;

        // Unload old scene
        AsyncOperation unload = SceneManager.UnloadSceneAsync(SceneManager.GetActiveScene());

        // Wait until it's finished unloading
        while (!unload.isDone) yield return null;
        // --- THE COROUTINE STOPS HERE DURING THE 3RD LOADING --- //

        // Make the loading screen disappear
        sceneLoader.GetComponent<Animator>().SetTrigger("disappear");

        // Wait until the disappearing animation is over, then destroy the SceneLoader object
        // which I set to DontDestroyOnLoad before
        yield return new WaitForSeconds(LoadingScreen_disappearTime);

        Destroy(sceneLoader);
        isLoadingScene = false;
    }

Only during the 3rd loading, right after the while (!unload.isDone) yield return null; line the coroutine just stops executing (I know it because I inserted a Debug.Log inside the while loop and it got called, but I inserted one right after and it did NOT get called).

Any suggestions?

2

So, from your description and code, my best guess is that where you set unload.isDone is where your problem is. I don’t think it’s possible to tell where you went wrong without looking at that part.

3

Shouldn’t you cache the “old scene” at the start of the coroutine instead of using GetActiveScene() after the other scene has finished loading? I think there’s a race condition where you’re trying to load and unload the same scene.

4

Tried adding Scene oldScene = SceneManager.GetActiveScene() after line 35 and then changing line 62 to AsyncOperation unload = SceneManager.UnloadSceneAsync(oldScene), didn’t change a thing. Issue still remains.