From the factory the BT is always open to connect. You can turn this off in the settings of the device. However, this makes it a bit more ‘complicated’, when you want to use that function yourself. By the way, how often do you use BT with the Beosound Core, which is a network device and has several other ways to be used. If seldom - or even never - you can deactivate BT there (at least there). Maybe the best way would be to talk with your neighbours, invite them over to show how annoying it is, when someone else suddently starts playing music in your house. MM

I don’t know the Core that well. However, I thought you could select local sources in the configure menu. If you can, you should be able to flick BT music off? Also, a factory reset and re-install but without Chromcast activated may help? I suspect either your neighbours are playing you by casting to the Core, or they once inadvertently connected and every now @nd again, mistakenly cast to your core without knowing it?

It must be bluetooth.  To cast or airplay to it they would have to be on the same network.  If they are that would be a concern unless you gave them your wi-fi password. If they are using bluetooth to play music through your Core, you should be able to go into Product Settings -> Paired Bluetooth devices, select the device and unpair it. For a product of the Core age, it is probably Product Settings -> Configure -> Bluetooth -> Removed Paired Devices