[Forage]

Kodi 'looses' libcec control as soon as I try to hook into it. Running "cec-client" through ssh is sufficient to prevent further control of Kodi by using my TV remote. Button presses are, however, still registered by looking at the output of "cec-client". Kodi just doesn't respond any more. Closing "cec-client" doesn't fix it, nor switching active source. Only a reboot gives me back control.

This is how it's always been, you can't use cec-client without risk of breaking the communication link Kodi already has with CEC.

See here, which did link to a reply from Pulse-Eight on their forum explaining why cec-client breaks Kodi but unfortunately the forum is no longer available.

So it was just sheer luck that it has been working in the past? I find that very unfortunate. Too bad the forum is gone for some more background information. I guess that means I'll have start the bisecting anyway to see what has changed to make it break more consistently now.
I want to use it for a second CEC adapter that isn't even used by Kodi but that causes the other one to break as well.