We found a working setup for the screen standby audio-loss issue after an OS image update. Notably, the version roll back to the previous disk-snapshot only made the behavior become intermittent on some pi3B+. Setup process to fix audio:

1. Open audio control panel, and disable all audio output devices

2. In a terminal run: rm ~/.config/pulse/*

3. Shutdown to power-off pi

4. Power-on pi, and login

5. Open audio control panel, and select analog output (make sure other output disabled)

6. Check selected input and outputs screen

7. Click close, and Reboot system

Do not power off the HDMI LCD at any time during this process, or you will need to redo this from step 1.

However, once the above setup is complete one may simply reboot the desktop to get audio again.