If its to be used on a S905, ES gives problems when using CEC, the program will segfault when it returns from a game, at least this was when I tried it a few months back, I had to remove CEC support for my build when this happened. And my 2 cents, I also do not see the benefit from using CEC with ES .
I understand the motivation for Retropie since ES is basically your gui and if you just want to watch a movie it can be annoying to get a controller / keyboard everytime you want to switch to Kodi. But since in my build Kodi is controllable by remote & IMHO if I want to play a game I connect a gamepad anyway so I don't really understand the actual usecase.
So I've checked your libcec version and it's 4.x too but still an quite old version compared to the recent LE 9 one. I never really used cec so how can I trigger the error? Is it enough to run ES with enabled cec on a tv with cec support?