Turning OFF CEC would be my suggestion.

I had a recent case where a Samsung TV power command would trigger a SONY TV in another room via CEC connected through a Blue-Ray player, connected to an HDMI splitter. I used a CEC blocker to the Samsung TV. There is no control system installed. It was very frustrating because only the Samsung Power ON command was forwarded, Samsung Power OFF had no effect on the Sony TV.

Originally, the system was fine. I suspect that an update of something enabled the CEC mess -- likely the Sony TV. I had other connectivity issues with that TV that changed over time and seemed to be CEC related.

I've had issues with Comcast cable box updates turning things ON in the middle of the night. Note that you can schedule Comcast updates. It would pay to check if the cable box update time window correlates with any of these events.