You could add a CEC-less adapter to the HDMI cable connecting the device and it would have the same effect but be limited to that single device.
https://www.amazon.com/BlueRigger-HDMI-CEC-Less-Adapter/dp/B07BFL8TM8
Then get yourself one of these for the cable box.
https://www.amazon.com/BlueRigger-HDMI-CEC-Less-Adapter/dp/B07BFL8TM8
Removes the CEC signal.
Seems obvious that the issue is introduced by the cable box. You can buy CEC-less HDMI adapters from Amazon that might help with the issue. Otherwise report the issue to your cable company and ask them to replace the box and see if you have the same issue with a new box.
It didn’t work in the fios box, but this CEC Less HDMI from Amazon did the trick; thanks to u/FlickFreak
If you find a connected HDMI device is causing it then you can use an HDMI CEC-less adapter to solve the issue.
I have the same tv and was having similar issues. After many hours across multiple days of troubleshooting, I found the problem to be CEC. I had to get a CEC less adapter for a few devices because they were causing issues across all inputs. The shield, my PC, and my Mister FPGA all caused major issues due to CEC.
The shield doesn't turn off CEC completely even when it's disabled. I wasn't able to figure out a way to turn it off in Windows 11. No option at all on the Mister.
This adapter won't pass the CEC signal at all. I would suggest getting 1 for your PC and the Shield.
If you want to cheap out, you can also mod an HDMI cable by removing the pin that carrries the CEC signal but you probably need elf hands for that.