User can login only once, after that login fails

There is a problem with the function "drupal_get_form" which resides in "user_external_login". The information of the login form can't reach this function, so the login hangs. A fast fix of this problem is to change the following in the "site_network.authentication.inc" file:

52:        if (isset($account->uid)) {
53:             //user_external_login($account);

and after that add the following code

// Check if user is blocked or denied by access rules.
user_login_name_validate($form, $state, (array)$account);
if (form_get_errors()) {
// Invalid login.
return FALSE;
}

// Valid login.
global $user;
$user = $account;
user_authenticate_finalize($state['values']);

I am closing this issue, since it's for a Drupal version no longer supported.