Odd not sure what could be going on, best get @support to see if they have any ideas.They may want to know you network topology and hardware used for the network to debug.
HI sure, but I think there is nothing special The Core is connected to a 1Gbit network switch. The Chromecast is connected with a UGREEN Ethernet Adapter to the same switch. Because of structural reasons the switch is connected with a powerline-set with a Fritz.Box 7590.
As mentioned in our Networking Guide, we typically recommend against powerline adapters when possible as we’ve seen this type of behavior stem from them. It’s hard to say just yet if that is the cause of what you’re experiencing, but it is something to keep in mind as we move forward with troubleshooting.
What is the model of the switch you’re using? Is it managed?
If you use WiFi instead of the Ethernet adapter does the same behavior occur here?
it is a simple 8port Netgear unmanaged Switch. On friday I will try to replace the Chromecast by a Raspberry running Roopie (yeah) and try to use wifi for the Chromecast.