messages in error log

My error_log file is full with such messages, although the plugin settings page works well and the tables mentioned do exist. How come?

(dcw_ is my table prefix)

[21-Sep-2015 17:53:16 UTC] WordPress database error Table ‘mydb.dcw_redirection_404’ doesn’t exist for query SHOW FULL COLUMNS FROM dcw_redirection_404 made by require(‘wp-blog-header.php’), require_once(‘wp-includes/template-loader.php’), do_action(‘template_redirect’), call_user_func_array, WordPress_Module->template_redirect, RE_404::create

[21-Sep-2015 17:53:19 UTC] WordPress database error Table ‘mydb.dcw_redirection_items’ doesn’t exist for query SELECT dcw_redirection_items.*,dcw_redirection_groups.position AS group_pos FROM dcw_redirection_items INNER JOIN dcw_redirection_groups ON dcw_redirection_groups.id=dcw_redirection_items.group_id AND dcw_redirection_groups.status=’enabled’ AND dcw_redirection_groups.module_id=1 WHERE (dcw_redirection_items.regex=1 OR dcw_redirection_items.url=’/category/%D7%91%D7%95%D7%98%D7%99%D7%A7-%D7%94%D7%9E%D7%A2%D7%A6%D7%91%D7%99%D7%9D’) made by require(‘wp-blog-header.php’), require_once(‘wp-load.php’), require_once(‘/home/user/wp-config.php’), require_once(‘wp-settings.php’), do_action(‘init’), call_user_func_array, WordPress_Module->init, Red_Item::get_for_url

https://ww.wp.xz.cn/plugins/redirection/