Firebase - "Object reference not set to an instance of an object" - how to further analyse it?

Hello everyone,

I am using Firebase for authentication and for storing data. Now I have the curious problem that this initialization fails sometimes with the error "Object reference not set to an instance of an object" (with the InitializeFirebase method) and I have no idea how to get to the root cause.

This is my code:

 public class FirebaseManagerAuth : MonoBehaviour
 {
     public static FirebaseManagerAuth instance;
     [SerializeField] private PlayerDataSO playerData;
 
     //Firebase variables
     [Header("Firebase")]
     public DependencyStatus dependencyStatus;
     public FirebaseAuth fbAuth;
     public FirebaseUser fbUser;
 
 
     void Awake()
     {
         //Check that all of the necessary dependencies for Firebase are present on the system
         FirebaseApp.CheckAndFixDependenciesAsync().ContinueWith(task =>
         {
             dependencyStatus = task.Result;
             if (dependencyStatus == DependencyStatus.Available)
             {
                 //If they are avalible Initialize Firebase
                 InitializeFirebase();
             }
             else
             {
                 Debug.LogError("Could not resolve all Firebase dependencies: " + dependencyStatus);
             }
         });
 
         if (instance == null)
         {
             instance = this;
             Debug.Log("FirebaseManagerAuth - awake - instance was null");
         }
         else if (instance != null)
         {
             Debug.Log("Instance already exists, destroying object!");
             Destroy(this);
         }
     }
   
     private void InitializeFirebase()
     {
         try
         {
             fbAuth = FirebaseAuth.DefaultInstance; **ERROR HAPPENS HERE**
         }
         catch (Exception e)
         {
             Debug.Log("Gotcha - AUTH! " + e.Message); 
             //throw e;
         }
         if (fbAuth == null)
             Debug.Log("INIT FirebaseManagerAUTH + fbAuth = null");
     }

And this the output:

 Gotcha - AUTH! Object reference not set to an instance of an object
 UnityEngine.Debug:Log (object)
 FirebaseManagerAuth:InitializeFirebase () (at Assets/Scripts/FirebaseManagerAuth.cs:68)
 FirebaseManagerAuth:<Awake>b__5_0 (System.Threading.Tasks.Task`1<Firebase.DependencyStatus>) (at Assets/Scripts/FirebaseManagerAuth.cs:32)
 System.Threading._ThreadPoolWaitCallback:PerformWaitCallback ()

Unfortunately, I have no idea why this reference is not always set correctly and how to further analyse it, since some "Firebase magic" happens here which I cannot control directly.

I would be very glad for any advice, since it fully blocks my development at the moment...