Hello Stanislav Mitov !

Usually, this trouble appears when something was wrong with the installation / backup problems. So you need to backup your current UNA database and apply the following queries:

delete FROM `bx_timeline_handlers` WHERE `group` like 'bx_ads%';

delete FROM `sys_alerts` WHERE `unit` like 'bx_ads%';

delete FROM `bx_notifications_handlers` WHERE `alert_unit` like 'bx_ads%';