After migrating a few old servers to new one's we renamed the old to "old-example.com" and added in new ones (new hostnames as well) with display names "example.com". We had to rename because the interface wouldn't allow us to use this a display name since it is a duplicate.

We then disabled the old servers in Zabbix, but leaving them for history purposes.

The Zabbix-agent on the old server is configured as hostname 'example.com' and somehow managed to be added to Zabbix again. Editing the host (e.g. disabling it again) results in an error:

Host with the same visible name "acc.monet-ssd.nl" already exists. [hosts.php:547 ? CFrontendApiWrapper->update() ? CApiWrapper->__call() ? CFrontendApiWrapper->callMethod() ? CApiWrapper->callMethod() ? CFrontendApiWrapper->callClientMethod() ? CLocalApiClient->callMethod() ? call_user_func_array() ? CHost->update() ? CHost->validateUpdate() ? CApiService::exception() in include/classes/api/services/CHost.php:1888]

The discovery shouldn't be creating hosts that have duplicate (display)names should it?