a) In your option for "clearing cache memory", in both the link and the PDF, you choose "clear data" instead of "clear cache". Those are two distinct choices. Do you really mean "clear data" or "clear cache" ???
I chose "clear cache" and it made no difference as far as the sound.
b) The "entering and exiting HDMI mode" method did work. However, just turning the unit off and on again turns the sound off again and then I need to again do the little "HDMI enter/ HDMI exit" dance. That's rather annoying to have to do that every time. Is there any chance that the next firmware update will correct this problem permanently ?