I've been testing Multiview heavily in my living room, for many hours a day, without any issues. I haven't had any hiccups and I've tried many channel configurations. That's with a 1st gen AppleTV 4K, connected to a Sonos home theater setup. It runs very smoothly.
On my bedroom TV however I just started testing Muttview, and after about 15 minutes of playback, it starts to stutters, very badly. This happens for a few seconds then resumes normally. But it comes back every couple of minutes. It happens regardless of which channel is focused, it's happened with OTA channels, TVE and custom channels (Fubo-VLC bridge.). These same channels play fine when played as normal live TV, without Multiview. But in Multiview mode, after a few minutes, it starts to stutter repeatedly and it's hard to ignore. I captured video from my phone of what it sounds like:
What's odd is that this model is an AppleTV 4K (2nd gen, 64 GB) which its newer than the one in the living room, that doesn't have this issue. It's on the release of tvOS 26, the latest TestFlight of Channels, and is hard-wired using Ethernet. I've had no other networking or streaming issues. I tried rebooting the AppleTV, didn't help. In Channel's Advanced settings I also tried troubleshooting by toggling off Surround Sound settings, and also Audio Driver back to Legacy. Neither made a difference, I'm not sure what else I can try. I submitted diagnostics from the AppleTV though. Happy to test anything anyone suggests!