Thanks for posting the video. That's classic pixelation and macro blocking caused by packet loss on the multicast channel, and the artifacts are where the box isn't able to "fill in the blanks" - a bit like missing pages in a book, where you can just about work out where the story is going but not how it got there.
If the box is Wi-Fi connected, it could be suffering poor reception but as you mention a 4K stream is playing it suggests the problem might be specific to the multicast throughput via from the network via the hub.
If you'd like me to check please ping me your TV box serial number in a DM and I'll take a look.
Cheers
David
