OK… go to “Devices” → Select “Entities” and find your long list of available entities.
Now, it happens, that during the setup - you just forget to set the area for some devices / or for some entities.
I know - you can try to manage that within the device section - when you change the area for the whole device… but wth - why can I select the entities - and activate / deactivate them - but not change their area in “one step” ?
I have to do this for each device individually… 