Why does this Firebase web authentication function 'onAuthStateChanged' occasionally not fire?

The intention of this code is to use Firebase for Web (JavaScript) and automatically sign-up visitors to the website as an anonymous user, however if they created an account using email and the anonymous sign-in is ignored.

Symptoms of this issue are:

• At random, maybe 2% of the time, the function 'onAuthStateChanged' does not fire at all.
• Refreshing the browser does not fix the issue
• Closing and reopening the tab does fix the issue
• Mostly happens on the Chrome iOS app, but not only.

When this happens, the debug statements look like this:

• loaded 4

• loaded 5

• loaded 6

• loaded 7

• loaded 8

~98% of the time this code works as intended but around 2% of the time is does not work at all and the user must close and reopen the tab and I can't figure out why. Does anyone know what's wrong?

    console.log("loaded 4");
    const analytics = getAnalytics(app);
    console.log("loaded 5");
    const db = getFirestore(app);
    console.log("loaded 6");
    const functions = getFunctions(app);
    console.log("loaded 7");
    const auth = getAuth();
    console.log("loaded 8");

    onAuthStateChanged(auth, (user) => {
      console.log("initiate on auth state change")

      if (user) {
        console.log("signed is as something")
        fuctionToLoadStuff();

        let uid = user.uid;
        const isAnon = user.isAnonymous;
        if (isAnon == true) {
          console.log("User is signed in anonymously as " + uid);
          annonUserStuff(uid);

        } else {
          console.log("User is signed into an account as " + uid);
          getProfile(uid);
        }
      } else {
        console.log("signed is as nothing");
        signInAnonymously(auth)
          .then(() => {
            const uid = auth.currentUser.uid;
            console.log("Anon user acct created");
          functionForANewAnonUser(uid);
          })
          .catch((error) => {
            const errorCode = error.code;
            const errorMessage = error.message;
            console.log(errorMessage);
          });
      }
    });