Can CANBUS block the audio CANBUS signals?

[Kinighit]

Hi folks,

I'm having a bit of 'mare with my 2002 V70, but this should relate to any Volvo with a HU-803.

I've swapped out the old head unit to fit a double din Pioneer with DAB and Android Auto and rear camera (to be fitted when drier). Everything works wonderfully, except the centre speaker from the Dolby Pro Logic (I just need to bridge the feeds at a later date) and the steering controls!
I have searched for weeks through these and other forums and can't find an answer about the steering controls relevant to the UK, especially one that is from the last 4 years.

I've used a kit from a company called InCarTec in the UK, which includes a colour matched facia and the wiring harness including the CANBUS interface and the DIN plug to use the OEM amp, harness part number is 39-VOL-02.
Everything has been set up as per the instructions although I'm not using the speed pulse output (not required on this Pioneer) or the CAN ignition but still no steering controls, I've even had a replacement CANBUS interface. It's stumped the manufacturer too!

Using an obd2 computer I can see a CEM 1A59 Fault code, which is Comms with Audio Unit. Does anyone know if this essentially blocks the CANBUS signal for the steering wheel controls?
I've read I can go to a dealer and have the audio module "divorced" from the car and this can clear the fault, but I'm not near one for months due to work commitments.

Has anyone in the UK used this kit before and been successful? Or recommend a CANBUS kit that works with a DIN plug included so I don't need to splice cables?

Thanks