In addition to the above, I logged into the web interface to see if that worked. It does, but It keeps popping up socket disconnected errors.
Try changing the HDMI cable first
Also make sure you push the cable in firmly.
Sam
It will be written to /boot/ when you use the respective tag
Thanks fzinken, how do I access it? I thought I used to be able to get to the logs location through explorer, but I canāt access a thing using my windows laptop anymore, all I get is āYou do not have permissionā¦blah blah blahā
Swapping out the hdmi cable has sorted the occasional black screens.
Great.
May have spoken too soon, kids have reported more black screens, and I saw one for the first time this morning. 
Ok ā so I assume this was after some power cycle
Is the Vero being turned off / suspended at night?
No it runs all the time Sam, no suspend, no power cycles. The only time it ever power cycles is if it crashes, which is pretty rare.
Iām sure when people were first asking for a shutdown/suspend feature, I remember you saying that the Vero was designed to run all the time with no issue. So thatās how I have been running it. Also, I recall you saying that suspend just shuts off the hdmi anyway.
Iām not ruling out the AVR yet either, it is like 6 years old.
I may take the cover off and put some heat sinks on the ICās on the hdmi board.
Yes thatās correct. You can keep the device running permanently.
My only other suggestion would be to enable the HPD Lock setting; otherwise we need to look in to the AVR