HDMI CEC is the bane of my (home theater) existence.
Which device just woke every other device up at 4am?
Which device just shut everything down while I was in the middle of a movie?
And are they the same device?
CEC and eARC piss me off to no end - it was all working perfectly for over a year and now the receiver refuses to cooperate (or maybe it's the TV, who knows) and you have to cycle things by hand like a meanderthal.
A Raspberry Pi can help debug and fix HDMI CEC flakiness, with the right cable - https://johnlian.net/posts/hdmi-cec/