WordPress database error: [Illegal mix of collations (utf8mb4_unicode_520_ci,IMPLICIT) and (utf8mb4_unicode_ci,IMPLICIT) for operation '=']
INSERT IGNORE INTO fs_mailpoet_subscribers (wp_user_id, email, status, created_at, `source`, deleted_at) SELECT wu.id, wu.user_email, 'unconfirmed', CURRENT_TIMESTAMP(), 'wordpress_user', null FROM fs_users wu LEFT JOIN fs_mailpoet_subscribers s ON wu.id = s.wp_user_id LEFT JOIN fs_mailpoet_subscribers existingSubscriber ON wu.user_email = existingSubscriber.email WHERE s.wp_user_id IS NULL AND wu.user_email != '' ON DUPLICATE KEY UPDATE wp_user_id = wu.id, deleted_at = IF( existingSubscriber.`source` = 'wordpress_user_deleted' AND existingSubscriber.deleted_at IS NOT NULL, NULL, existingSubscriber.deleted_at ), `source` = IF( existingSubscriber.`source` = 'wordpress_user_deleted', 'wordpress_user', existingSubscriber.`source` )