How to fix my onFormSubmit function with state?

Question

There is part of my Component:

 const { id } = useParams();
  const [name, inputName] = useState("");
  const [email, inputEmail] = useState("");
  const [start, inputStart] = useState("");
  const [end, inputEnd] = useState("");

  const [errorNameEmpty, isErrorNameEmpty] = useState(false);
  const [errorEmailValid, iserrorEmailValid] = useState(false);
  const [errorStartEmpty, isErrorStartEmpty] = useState(false);
  const [errorEndEmpty, isErrorEndEmpty] = useState(false);
  const [errorDate, isErrorDate] = useState(false);
  const [sendData, setSendData] = useState(false);

  const validEmail = new RegExp(/^\S+@\S+\.\S+$/);

  const onFormSubmit = (e) => {
    e.preventDefault();
    let startDate = new Date(start).getTime();
    let endDate = new Date(end).getTime();

    if (startDate > endDate || startDate === endDate) {
      isErrorDate(true);
    } else {
      isErrorDate(false);
    }

    if (name === "") {
      isErrorNameEmpty(true);
    } else {
      isErrorNameEmpty(false);
    }

    if (email === "") {
      iserrorEmailValid(true);
    } else if (!validEmail.test(email)) {
      iserrorEmailValid(true);
    } else {
      iserrorEmailValid(false);
    }

    if (start === "") {
      isErrorStartEmpty(true);
    } else {
      isErrorStartEmpty(false);
    }

    if (end === "") {
      isErrorEndEmpty(true);
    } else {
      isErrorEndEmpty(false);
    }

    if (
      errorNameEmpty ||
      errorEmailValid ||
      errorStartEmpty ||
      errorEndEmpty ||
      errorDate ||
      sendData
    ) {
      setSendData(false);
      console.log("Net");
    } else {
      setSendData(true);
      console.log("Da");
    }

    let newIntern = {
      name: name,
      email: email,
      internshipStart: start + "T00:00+00Z",
      internshipEnd: end + "T00:00+00Z",
    };

    if (sendData) {
      const requestOptions = {
        method: "PUT",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify(newIntern),
      };
      fetch(`http://localhost:3001/interns/${id}`, requestOptions).then(
        (response) => response.json()
      );
      console.log("Good");
    } else {
    }
  };

onFormSubmit is a function that fires when the button is clicked. I want that if there are no errors (that is, when all states that store error states = false) my fetch will work, and in the case when at least one state has an error = true then fetch will not be performed. Now after the first click, when I deliberately make a mistake in my form, the function works fine (fetch does not work), but immediately changes sendData = true. and if you click again, then fetch will work. I don't understand why sendData is set to true after the first call of the function.