No notification after manuel deleting downtime


I have a little problem with the downtime of Icinga2.
The problem is, that i can send the downtime, but if I delete it manual and a critical problem occurs (before i stop the downtime) the history says that there get send a notification, but the (e-mail) notification doesn`t reach me.
But if the time of the Downtime is over the notification works as expected again.
The notification also works as expected if the critical occurs after I close the downtime manual and before the Downtime will end automatically.
So does anyone know what the problem can be in this case?

Many thanks in advance