React form submit triggers two times - reactjs

Question

I have React login form. The problem is form submit is called two times. I dont understand it. Can somebody tell me please why? Thanks a lot.
import React from "react"
import LoginErrors from "./LoginErrors"
import LoginSuccess from "./LoginSuccess"
import axios from 'axios'
import { withRouter } from "react-router-dom";
class Login extends React.Component
{
constructor(props)
{
super(props)
this.state = {
name: '',
password: '',
errors: [],
success: []
}
}
changeName = e =>
{
this.setState({name: e.target.value});
}
changePassword = e =>
{
this.setState({password: e.target.value});
}
sendData(e)
{
e.preventDefault();
this.setState({'errors': [], 'success': []});
let formData = new FormData();
formData.set('name', this.state.name);
formData.set('password', this.state.password);
axios({
method: 'POST',
url: 'http://localhost:8000/login',
data: formData,
headers: {
'Content-Type': 'text/html',
'X-Requested-With': 'XMLHttpRequest',
}
})
.then(response => {
// ? returns undefined if variable is undefined
if( response.data?.errors?.length )
{
this.setState({errors: response.data.errors})
}
if( response.data?.success?.length )
{
let data = response.data
this.props.setAccessToken(data.token)
this.props.setUserName(data.user.name)
this.props.history.push('/')
}
})
.catch(response => {
this.setState({errors: ['Login fails. Try it again later please.']})
});
}
render() {
return (
<div className="row justify-content-md-center">
<div className="col-sm-12 col-md-6">
<div id="loginForm">
<h2 className="">Login</h2>
<LoginSuccess success={this.state.success} />
<LoginErrors errors={this.state.errors} sendParentMessage={this.handleErrorsChildMessage} />
<form onSubmit={e => {this.sendData(e)}}>
<div className="form-group">
<label htmlFor="name">Name</label>
<input ref={this.email} name="name" className="form-control" type="text" onChange={this.changeName} />
</div>
<div className="form-group">
<label htmlFor="password">Heslo</label>
<input ref={this.password} name="password" className="form-control" type="password" onChange={this.changePassword} />
</div>
<div className="form-group">
<button name="sbmt" className="btn btn-primary" type="submit">Odoslať</button>
</div>
</form>
</div>
</div>
</div>
);
}
}
So the problem is in axios preflyght request which is related to the CORS policy. But How to stop it?