I managed to upgrade my amp last night. I wasn’t sure it had worked but it says it’s running the new firmware.
This morning, when I’m not recording, TV comes on as normal, no issues.
Tonight, I turn the TV on mid recording and still no picture, however this time, changing the input on my amp and then changing it back again does fix the issue.
So not perfect, but at least I can get it to show the picture again now. Thanks for your help!