The Civi TY mailer is logging errors, maybe on each send?
Check if this has to do with new templates or with CiviCRM upgrade of Jun 29th
Example: DB Error: constraint violation
INSERT INTO `civicrm_mailing_event_queue` (`job_id` , `email_id` , `contact_id` , `hash` ) VALUES ( 41940228 , 24599656 , 24387446 , '2c45e8e0389fe146' ) [nativecode=1452 ** Cannot add or update a child row: a foreign key constraint fails (`civicrm`.`civicrm_mailing_event_queue`, CONSTRAINT `FK_civicrm_mailing_event_queue_email_id` FOREIGN KEY (`email_id`)
civicrm_email (id) ON DELETE SET NULL)]