Doing my monthly check, i see a couple of those:
[27-Dec-2018 16:59:27 UTC] WordPress database error Duplicate entry '76-topic-3-' for key 'fld_group_unq' for query INSERT INTO `wp_wpforo_subscribes` (`itemid`, `type`, `confirmkey`, `userid`, `active`, `user_name`, `user_email`) VALUES (76, 'topic', 'e4fa784a760805e44b98a219edc45cb6', 3, 1, '', '') made by require('wp-blog-header.php'), require_once('wp-load.php'), require_once('wp-config.php'), require_once('wp-settings.php'), do_action('wp_loaded'), WP_Hook->do_action, WP_Hook->apply_filters, wpforo_actions, wpForoTopic->add, do_action('wpforo_after_add_topic'), WP_Hook->do_action, WP_Hook->apply_filters, wpforo_topic_auto_subscribe, wpForoSubscribe->add
Any ideas ?
Just ignore it. For some reason some user tried to subscribe for the same topic twice and the database generated duplication error. I don't see any issue here. The UX doesn't allow to do this, but somehow he/she find a way to press subscribe button or check subscribe checkbox again. We'll investigate it. Maybe the page was cached and the Subscribe button was not changed to Unsubscribe button or he/she did double click.
I think you are planting db errors just for me....