[firebase_messaging]: App sometimes crashes on background messages due to FirebaseAuth

[Navil]

Is there an existing issue for this?

• I have searched the existing issues.

Are you aware of the differences between iOS and Android background message handling?

• I understand that iOS and Android background messages behave differently, and I've designed my application with that in mind.

Do you have an active Apple Developer account?

• I have an active Apple Developer account.

Are you using a physical iOS device to test background messages?

• I am using a physical iOS device to test background messages.

Have you enabled "Remote Notifications" & "Background Mode" (Checking options for "Background Processing" & "Remote Notifications") in your app's Xcode project?

Have you created an APNs key in your Apple Developer account & uploaded this APNs key to your Firebase console?

Have you disabled method swizzling for Firebase in your app?

The key is not in my info.plist file

Are you sending messages to your app from the Firebase Admin SDK?

const message = {
        notification: {
          title: title,
          body: messageData.text,
        },
        data: {
          ...messageData,
          badge: String(numMessages),
        },
        apns: {
          payload: {
            aps: {
              "content-available": 1,
              badge: numMessages,
            },
          },
        },
        token: token,
      };

      if (!admin) {
        admin = require("firebase-admin");
        const firebase_credentials = context.values.get("firebase_credentials");
        const doc = JSON.parse(firebase_credentials);
        admin.initializeApp({
          credential: admin.credential.cert(doc),
        });
      }
      await admin.messaging().send(message);

Have you requested permission from the user to receive notifications?

• I have the relevant permission to receive notifications.

Have you used the 'Console' application on your macOS device to check if the iOS device's system is throttling your background messages?

Not relevant

Additional context and comments

My Flutter app (production) shows crashes when users receive notifications. This is nothing I can recreate, and it "only" happens to around 100 users.

According to my backend logs, this crash seems to happen when a notification is being sent to a user. My assumption is, that this is happening while the app is in the background.

Normal notifications (and background notifications) work fine in most cases.

I am currently not having "Background processing" enabled in Xcode, as I followed the documentation when setting up Firebase Messaging.