Also with my Sony Bravia I have troubles with CEC pulse eight, RB pi4 and Kodi 18.4 Leia.
It seems that remote control works just after a fresh install of LibreELEC-RPi4.arm-9.1.501.img, but then, after switchin off and on again, it stopped doing its work... Also downgrading to LibreELEC-RPi4.arm-9.1.002.img does the same (working at first run, then stopping).
TV and remote perfectly working with RB pi2 and 3 and OpenElec, Kodi 16.1 Jarvis.
Bravia Sync (settings for CEC) sometimes does not see RB pi 4 and sometimes sees it (but also in this case, remote control not working).
Thanks a lot