Been suffering with much the same issue on a TCL 6-series Roku TV trying to get a Sony soundbar to remain connected for more than 24 hours
I came to the conclusion that the conflict occurring was because of a slow ‘handshake’ from a soundbar is elbowed out of the way by the other CEC handshakes trying to take place at TV start-up. In some circumstances it will mean eARC becomes Inactive, and in worst-case, will mean no CEC is recognized at all.
That left me thinking “How can I isolate the eARC handshake, and then bring up what I want connected after that?” That led me to set the Power On input setting to be the soundbar, and in doing so, if the eARC is not active, I would the see the handshake take place. If the eARC connection is still Active, then you don’t see the handshake, but do still see the soundbar’s volume control in the top corner to confirm the soundbar is live.
Leaving all other CEC settings in place - just one in my case with a paucity of HDMI connections on my particular model - it is then just a couple of input presses on my remote to get my FireTV cube to cut back across with its own input and the sound is back and steady for the duration of the viewing. Setting up this handshake to happen every time you turn on means it starts a fresh session each time and you shouldn’t have to worry that it may or may not be there from last time you used the TV.
I appreciate that this is less than ideal, but it has seemed to work so far without any issues since setting it up a week ago. It leads me to wonder is a delayed handshake built into the start-up of a number of milliseconds between eARC and other HDMI inputs could be a possible solution that could resolve issues across the TCL brand and for which seemingly no resolution has been found.
Good luck should anyone care to try this, and I’d very much appreciate any feedback if it helps in any way.
