Sony X900F and Onkyo AV receiver ARC handshake issues

[JPK]

Hoping someone might be able to assist here.

One of my setups is a 2.1 system with a Sony X900F and an Onkyo TX-RZ710. Have them connected via ARC HDMI and have satellite box and BD player connected through the AV receiver as per normal. It is all in a different room from my 'media rack' with remote extenders for the receiver and BD player etc. I am using a 25ft Blue Jeans BJC Series-3A Active HDMI cable.

All ARC and CEC settings are as they should be between the TV and receiver.

Had an array of issues recently. Starting from when the satellite box was turned off before anything else. After turning on the TV had major issues with it running TV speakers and the receiver together and wasn't letting me select audio system in the TV's settings and giving a communication error when I tried. It appears it sent some sort of signal (somehow) back to receiver.

Fixed this particular issue by removing the powered HDMI splitter after the satellite box and being at peace with only having the signal going to one room (the 2.1 room above). I also removed another 4K splitter that was splitting the Xbox One X signal. Both were working fine initially.
Tried switching the EID settings on both as part of the trial and error fix I tried to do.

I also removed the HDMI cable from both restarted, turned off, plugged the cable back in on both ends and restarted.

At this stage I have this:
- TV remote switches on/off AV receiver as it should
- Sound is obviously fine when using anything external going through the receiver (Satellite box, BD player)
- TV remote can intermittently control receiver volume. Even when satellite box is selected through receiver (HDMI 3 (ARC) selected)
- Netflix app never sends sound back to the receiver, neither does Amazon Prime or Tidal
- Disney+ intermittently sends sound back
- The interface sounds on the Android OS send sound back through the receiver

Note: Some of the intermittent issues change if I hard boot the TV and/or switch the TV (and by association the receiver) on/off and few times.

I highly doubt this is a cable issue and its stuck in a wall now anyway. As a backup I have a spare cat6 but I really don't think its worth going down that track yet.

I'm at my wits end and prepared to drop a bit of coin to fix it. My options at this point are:

1. Get another Apple TV 4K for this particular room and use the TV as a monitor.
2. Buy a Sony AV receiver (probably STRDH790) with 'Bravia Sync'. Presumably this will have a seamless same brand 'handshake' as both devices have 'Bravia Sync'?
3. Perhaps something else i'm missing?

As another side note, I actually had some issues with another X900F and Marantz SR6012 in my main setup but as it's only used as a monitor it didnt really matter disabling CEC and ARC for me. I have to turn the TV and receiver on separately. This makes me think it's a Sony issue?