Crazy thing is this was built in like the 1880s - my apartment building in Chicago is older than this castle. And the structure of the new castle was built out of brick, with stone cladding on the outside to give it the castle look.
They even dynamited actual medieval twin castle ruins that were on this site to make room for the new castle.
Are they using the same name (SSID) ? Some 2.4 only devices won't connect to a network with the same SSID on different bands. I have a separate IoT SSID available on 2.4 only for such devices (it's also on its own VLAN)