You give the answer in your question: Onkyo AV TX-333 is between the box and the TV.
The option to pass the volume control through HDMI-CEC is working if you have an amplifier between the receiver and the TV because the command sent are properly handled by the amplifier.
Very few TVs can understand those code and handle properly the volume control from the receiver.
Also you should not be fooled by the RCU, because some brand like VU+ offers a "small universal RCU" once you configure your TV code in the RCU you can turn the TV on/off from the VU+ RCU (without using HDMI-CEC) but the RCU also change the Volume+ / Volume- with the TV code and no longer the STB code (so once again nothing to do with the HDMI-CEC), so when adjusting the volume you think it goes from the VU+ to the TV but in fact it's not, the RCU send directly the TV RCU code for the audio volume.
If you test a direct connection between your TV and the SF8008 I am not convince that volume control will still work.
Edited by Pr2, 25 February 2022 - 14:29.
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VU+ Solo 4K: 2*DVB-S2 + 2*DVB-C/T/T2 (used in DVB-C) & Duo 4K: 2*DVB-S2X + DVB-C (FBC)
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