Notebook Audio

On this laptop the sound stops working on a regular basis.  All of a sudden there will be no sound output from the speakers or from headphones plugged in.  A red x will appear over the speaker icon in the tray. This happens once every few hours.

When I look in Device Manager / System Devices category / Intel Smart Sound Technology (Intel SST) OED will have a warning/exclamation icon over it.  I have attempted to disable the device, delete drivers, reinstall drivers etc from here but nothing will happen even after a long wait - the progress bar just repeats left to right.  The only thing that will get the sound to work again is holding down the power button for a few seconds to do a "hard shutdown", and switching on again.

Trying to do a restart or shutdown the usual way will either just restart without enabling sound or will sometimes blue screen.

I have installed the Intel® Driver & Support Assistant which says everything is up to date.

I have tried updating the BIOS to the latest version.

I have installed all available updates relating to the Realtek Audio driver in the HP Support Assistant app.

Windows Updates are up to date.

I ran the HP audio diagnostics upon bootup which ran OK.

Where do I start in fixing this?  Can you help?  Thanks.