Not sure if this is how its supposed to work, but I found an issue that I can reproduce every time.
Watching a live show and then pause it for a couple of minutes (can be as low as a minute), then unpause it to continue watching. Then when bringing up the guide to select a different channel/show, clicking the center button on the remote won't actually switch to that channel.
Only way to get it to switch is to press the home button, switch PIP back to full screen. Then click the back button to bring up the guide again (also, performing that steps kills the PIP which I don't believe should happen).
Can repro this in both stable and beta releases.