I am trying to sendEmailVerification using Firebase but it’s failing.

const handleSubmit = (e) => {
    e.preventDefault();
    fetch("http://localhost:4000/auth/register", {
      method: "POST",
      body: JSON.stringify({
        email,
        password,
      }),
      headers: {
        "Content-Type": "application/json",
      },
    })
    .then((res) => {
            return res.json()
    }).then((data) => {
        signInWithEmailAndPassword(auth, email, password);
    }).then(() => {
        console.log("data", auth.currentUser)
        sendEmailVerification(auth.currentUser)
        .then(() => {
            navigate('/')
        })

    }).catch((err) => {
        console.error(err);
    });
};

It seems like there’a delay to sendEmailVerification. If I sign up user1, no email verification is sent, but after I sign up user2, user1 email is then sent. Why is there a delay? I want the user email verification to be immediately sent after registration.