I’m running beta OS so issues are to be expected, but I thought I’d let you know in case this is something that Channels needs to fix when the OSs are released in (presumably) a couple of weeks.
The issue is that PiP video stops playing when navigating to another app. PiP works fine when Channels is the main app, but when moving to another the audio continues but the video stops. It is not completely frozen, it kind of judders but doesn’t actually progress.
This occurs in the release candidate too. Surprised this thread hasn’t had any attention yet!
Experiencing the same issue here. Seems to be only over the air HDHomeRun channels. IP channels seem to be fine.
You will need to switch to Settings > Playback > Advanced > Video Decoder: Experimental
My Video Driver was already set to Experimental.
I just had a play with different settings and it seems to be an issue with the Experimental Deinterlacing Mode. I switched this off and tried the Linear and Blend options. Playback in PIP seems to be fine with both of those other Deinterlacing modes.
I'm now not even seeing the PiP button on iOS. I've tried toggling the button to hide / show it in settings and force closing Channels, but the PiP button simply won't show. So, I sadly cannot test the effect of swapping to the experimental decoder.
This happened to me; I turned on the Experimental video driver and played something I had recorded from my library and the option returned to live TV. I’m not sure how to explain what happened, but it came back.
Yes, it does seem that turning on the experimental video driver brings back the button. It does also seem to fix the PiP problems I was experiencing previously. Some periodic audio distortions, but it does actually appear to work vs not working at all.
Yes, same experience on the iPad app, running on my M1 MacBook Pro. So I don’t think this issue was iOS 15 related, specifically, The PIP button disappeared when I updated the Channels app on my Mac. I don’t even think iOS 15 was out yet when it happened, and I hadn’t installed any version of iOS 15 yet.
But yes, turning on Experimental Video got the PIP button to reappear 
