@charlez This is indeed a confirmed error with the Check_Host Building Block (Baustein) and Gira Homserver 4.9
Also see this forum thread: https://knx-user-forum.de/forum/öffentlicher-bereich/knx-eib-forum/1392520-hs-fs-homeserver-4-9-logikbaustein-hostcheck-12242-geht-nicht-mehr
(I thought the maker of that Baustein is: Nills and maybe he takes a look at this forum also ;)
Roeller