Thanks.
I'll give it a try.
Hopefully it addresses another issue also:
Mute (all) button doesn't seem to mute "Alert Beeps" so when nearing an alert point, the background sound (2din) will drop out to play a "muted" sound resulting in no audio for several seconds.
I can prevent this happening by manually muting "Alert Beeps" after the mute all button is pressed. If that makes any sense. :)