How to remove the redirect when there is a data entry error when registering Wordpress?

Question

PHP

I have code that redirects to my modal window:

function redirect_reg_page() {  
    $reg_page  = home_url( '/#join_form' );  
    $page_viewed = basename($_SERVER['REQUEST_URI']);  
  
    if( $page_viewed == "wp-login.php?action=register" && $_SERVER['REQUEST_METHOD'] == 'GET') {  
        wp_redirect($reg_page);  
        exit;  
    }  
}  
add_action('init','redirect_reg_page');

In case of erroneous data entry in this modal window (registration) - it redirects to the standard registration page and an error message is displayed. How can I remove this redirect and why doesn't my redirect work in this situation?
The modal window itself has the following code:

<div class="popup">
            <p>Регистрация</p>
            <p>Пожалуйста заполните все поля</p>
      <form name="registerform" action="http://mysite.ru/wp-login.php?action=register" method="post" novalidate="novalidate">
  <div><p>
    <label for="user_login">Имя пользователя<br>
    <input id="firstname" type="text" name="user_login" value="" size="30"></label>
  </p></div>
  <div><p>
    <label for="user_email">E-mail<br>
    <input id="email" type="email" name="user_email" value="" size="30"></label>
  </p></div>
    <p id="reg_passmail">Пароль будет отправлен вам на e-mail.</p>
  <p class="submit"><input type="submit" name="wp-submit" id="wp-submit" class="button button-primary button-large" value="Регистрация"></p>
</form>
            
            <a class="close" href="#close"></a>
        </div>

The same situation with the entrance, with changing the password and getting the password. Please tell me how to fix? I'm trying to get rid of standard pages.

Answer 1

add_action('register_post', 'binda_register_fail_redirect', 99, 3);

function binda_register_fail_redirect( $sanitized_user_login, $user_email, $errors ){
    //this line is copied from register_new_user function of wp-login.php
    $errors = apply_filters( 'registration_errors', $errors, $sanitized_user_login, $user_email );
    //this if check is copied from register_new_user function of wp-login.php
    if ( $errors->get_error_code() ){
        //setup your custom URL for redirection
        $redirect_url = get_bloginfo('url') . '/registrace';
        //add error codes to custom redirection URL one by one
        foreach ( $errors->errors as $e => $m ){
            $redirect_url = add_query_arg( $e, '1', $redirect_url );    
        }
        //add finally, redirect to your custom page with all errors in attributes
        wp_redirect( $redirect_url );
        exit;   
    }
}

Answer 2

similar situation:
wordpress.stackexchange.com/questions/21765/redire...