As the Tanix TX9 Pro is a S912 SoC I am not sure if it can be disabled completely. At least not in suspend mode as CE does not have control over the bootloader bl301 blob. All other devices using Amlogic-ng image including bl301 injected and/or Odroid N2/C4 also support disable of CEC for Wakeup and can be set in Kodi CoreELEC Settings.
so set in config.ini (if not available in CE settings):
cec_func_config='0'
should disable it, yes
Different libCEC versions can be chosen by open a SSH connection and type:
remove any libcec config (default 4.0.4 will be used):
rm -rf /storage/.config/libcec-4.*.conf
enable libcec-4.0.5:
touch /storage/.config/libcec-4.0.5.conf
enable libcec-4.0.7:
touch /storage/.config/libcec-4.0.7.conf
When CEC is working after booting into CE and CEC is stopping working later it’s more related to libCEC then the CEC driver itself.