This is the same as reported by MatteN in the thread "RPi 4B - USB issues with latest kernel" however that thread was concerning a problem with a Mygica DVB USB stick, but then got added to by this particular problem.
Kodi is left running all the time and the LG is put into standby with the remote. After a while, the TV is restarted and the message no video signal appears. At this point I observe:-
Running top shows the status of kodi.bin is "Z" (zombie).
Systemctl stop kodi fails to stop main thread.
Systemctl reboot takes a very long time, but does fix the problem.
Switching to live tv and back to RPI does nothing.
The time the TV is in standby has an effect, if it is off for a short time the problem does not arise. In the attached log it took about 15 minutes for kodi to go into zombie state. This is probably because the TV may do Oled pixel cleaning when put into standby so does not go into deep sleep immediately.
The log was produced with debug turned on and libCEC chosen. The tv was put into standby about 01:00 and turned back on at 01:17.