Cannot delete API created Downtimes

Hi all,
Happy new year!
icinga2 --version
icinga2 - The Icinga 2 network monitoring daemon (version: r2.11.2-1)

A colleague created several Downtimes via an API user (which only has the permission to create downtimes for specific hosts). Unfortunately the time was not correct and I am trying to delete this downtimes. Unfortunately, I am not able to do this. If I try to delete them via Icingaweb2, I get the logs in icinga2.log like:
warning/Downtime: Cannot remove downtime 'xxxx' . It is owned by scheduled downtime object 'yyyy'.
So I tried to remove them via the api root user. After sending the curl I get the output
“code”: 200.0,
“status”: “Successfully removed downtime ‘xxxxx’.”
But again, the logs say the same. So the downtimes don’t disappear.
Anybody an idea, how to really delete them?



runtime downtimes which are created our of ScheduledDowntime object ranges cannot be deleted by the user. Only API created runtime downtimes are allowed in this regard.


Problem is, in our experience, the downtimes do not clean up after they are over: