filter login_errors not fired

login_errors filter will not work with the plugin. To customize error messages for custom errors please use lsw_login_errors filter.

Example given below.

add_filter( 'lsw_login_errors', 'lsw_custom_login_error_message', 10, 1 );
function lsw_custom_login_error_message( $error ){	
	$err_codes = $error->get_error_codes();
	if ( in_array( 'custom_error', $err_codes ) ) {
		$error = '<strong>ERROR</strong>: Custom error.';
	}
	return $error;
}