I have found a workaround that must be used at your own risk as I don't fully understand any other repercussions of this process. Also, being an intermittent fault I have not fully tested to see if this does indeed completely solve the problem.
I shall report back if it doesn’t work and is a waste of time.
If you are happy / confident to test it, try disabling the keyboard Mute, Volume and Play/Pause buttons. It does not affect the side volume control. Once these keys are disabled you will need to use the side hardware volume control (turn down to 0)
or software audio controls to mute.
Disable these four buttons by using “Device Manager”, expand “Human Interface Devices” and disable the second “HID-compliant consumer control device” in the list. There are two devices with the same name in the list and you will not be locked out if
you choose the wrong one but the aim is to stop just the audio touch cover keys from working. This device remains disabled if you remove / reconnect the touch cover.
If you do not understand what "Device Manager" does or do not know how to access it, then I would recommend that you do not change any settings in there. I would hate to be the person who gives advice that then screws up everyones brand new tablet.
If you try this please report back to the forum any results. Obviously this is
not a fix and we all still await Microsoft to release an update or hardware replacement.
Steve