Host not showing in "Monitoring" area of Zabbix web

[Pelzvieh]

A host I recently added is performing absolutely fine, generating data, triggering its triggers, etc. without problem.
However, it doesn't show up in several features specifically in the "Monitoring" area of Zabbix web:

• It does not appear in suggested list of auto-completing host fields, e.g. on Monitoring -> Latest Data -> Hosts
• It cannot be filtered for in Monitoring -> Problems, i. e. when entered manually in the host field, no problems are shown
• In Monitoring -> Dashboard, for any widget of type graph, its data are not showing, not even in the legend, although it is possible to create a data set entry for it

Even more strangely, it shows

• in the list shown with the "select" button next to host names
• in Monitoring -> Latest Data
• in Monitoring -> Dashboard, in widgets of type "Graph (classic)"

I'm really lost what makes this host special. AFAIR I did created it as a clone of an existing and correctly behaving host.