Device not found. Ensure your device is powered on and connected to your network.

[speakradmin]

This seems to happen randomly, not sure if anyone else is experiencing this. Restarting Plex seems to be the only way to remove the error.

Channels still stream fine but certain clients stuggle to discover the Live TV content. For example, Android Mobile doesn't seem to find the channels unless you manually navigate to them. ie they don't show up under the Live TV pinned section. Restarting Plex resolves this.

I've noticed that if a stream is stopped abruptly ie, closing a browser tab rather than stopping the player it's more likely to occur. In cases like this, channels will refuse to play for a while, sometimes recovering on it's own, sometimes requiring a restart of the plex-dvr-hls container. One of the other symptoms is that the activity widget shows a bunch of stale "Live TV - Session". Even though these streams have been stopped.

Then some minutes later it's gone but now it shows "Device not found"

Some googling shows that this was a common occurance some years back with various other hdhomerun emulators like xteve, telly and others but not sure if there's any other commonality

There does not seems to be anything obvious in the Plex logs or the plex-dvr-hls Docker container logs although I'm not really sure what I'm looking for.

I'd say the main difference is that when a stream abruptly ends, Plex fails to do this part:
Destroying metadata item 137813 (Channel 1@7AM)

Edit: Ok scratch that, it does eventually destroy the metadata but after that is when the Channel Source appears "Offline" to Plex