Not able to update "Used units" in Service Contract

[davide-alghi]

If I add a Ticket to the Service Contract (status "in progress") and set ticket status to "Accepted", the Service Contract's "Used units" field is not updated.

From code class ServiceContracts_ServiceContractsHandler_Handler {}

public function entityAfterSave(App\EventHandler $eventHandler)
{
...
      $dataReader = (new App\Db\Query())
	      ->select(['crmid'])
	      ->from('vtiger_crmentityrel')
	      ->where(['module' => 'ServiceContracts', 'relmodule' => 'HelpDesk', 'relcrmid' => $ticketId])
	      ->union(
		      (new App\Db\Query())
			      ->select(['relcrmid'])
			      ->from('vtiger_crmentityrel')
			      ->where(['relmodule' => 'ServiceContracts', 'module' => 'HelpDesk', 'crmid' => $ticketId])
	      )
	      ->createCommand()->query();
...
}

It seems it is required a M:M relation between Service Contract and Ticket modules.
I don't understand.