Hi cdowkes
Do you have the Stream box sound set to Follow Content? This setting generally prevents sounds dropping out.
For Sound issues go to Settings > Audio & Video > Audio Output > there are options > Follow Content, PCM 5.1 (HDMI only), and PCM 2.0
Netflix will always use Follow Content. Use 'Follow Content' for any bitstream audio like Atmos where it's available on content.
Also, loss of picture and/or sound can happen on live TV, but it's usually experienced on apps such as Netflix, Prime and Disney + and is generally due to a difference in frame rates.
Go to Settings >Audio & Video > Match frame rate
If it's set to ON then people do see a blackout/or hear a sound drop when the 360 or HDMI reconfigures for the difference in frame rate.(This is noticable on live TV when switching from adverts back to a program, or changing channels)
If it's set to the default (Off) then the box just accepts the frame rate difference which isn't noticeable by most users and shouldn't blank the screen out. (Either way try toggling this setting to see if it improves your issues)