Apple TV 4K automatically muting/un-muting (even after 'remote restarts' support article)

On first look this appears to have been asked and answered before in the following article: discussions.apple.com/thread/254130460

... but unfortunately it does NOT work i.e. when 'Volume Control' is enabled/On in the 'Remotes abnd Devices' menu any button press simply mutes/unmutes the TV volume. The only thing that seems to work is to double press the TV/Control Center button that allows you to close all open apps and go back to settings where you can turn of 'Volume Control'.

Also another issue encountered in the above mentioned article is step 3) as mentioned below:

1) First step: "1. Press and hold the TV/Control Center button and the Volume Down button  at

the same time. Hold the buttons down for about 5 seconds, or until the

status light on Apple TV turns off then turns on again. " .... this step works although you will have to wait about 10+ seconds

2) Second step: "2. Release the buttons, then wait 5–10 seconds. A Connection Lost notification will appear on your TV " ... again it may take more than 10 seconds but this also work and the "Connection Lost" does appear on the top right hand side of the TV screen.

3) Third step: "3. After your remote restarts, a Connected notification will appear on your TV screen. " ... this didn't seem to work at first no matter how long I wait, but eventually I figured out that if you power the remote via usb it will produce (force?) the "Connecting" notification.

Unfortunately in the above noted workaround in step 3 wasn't at all mentioned in the discussions.apple.com/thread/254130460 article which might explains why many likely clicked me too and only 8 clicked helpful; it may be helpful to restart the remote but unfortunately it doesn't fix the mute/unmute issue.

NB I personally have a Sony Bravia TV and I have tried connecting the Apple TV 4k to both the Sony TV directly and also via a Sony Receiver, neither of which works, and I have also tried using two separate HDMI cables. The odd thing is that I seem to recall everything was working just fine when I first got it.

Final attempt was to do a complete system rebuild of the Apple TV 4k and sadly this did nothing, apart from annoyingly deleting all apps and signin information.

UPS sing my iPhone remote app also doesn't work and the mute icon seems to be greyed out for some reason.

I just don't know what else I can possibly do.