Focus Mk4 infotainment problems

[_Jonesy_]

This is a bit of a niche one but I'm at a loss. Any suggestions welcome!

Mk4 Focus - 68 plate

Been having problems with the infotainment recently. It started when the audio tones (e.g door open) started playing through the tiny dashboard speakers rather than the normal system, and changed sound.

Now I can only get the phone to play through the dash speaker, making it inaudible when driving. When you adjust it it's now showing on screen as 'phone volume' when it normally says 'voice volume'.

I've also had a few random error messages, relating to ABS, auto-hold, active braking etc.

I thought all this pointed to a battery on the way out - however, I've tested it and it's reading 12.6V cold. I also tried hooking the car up to another good battery (fully charged) and the problem persists. I've held down the power and seek up button, I've done a full factory reset of the Sync, reset the BMS, tried a different phone and cable and I've disconnected the battery for 5 minutes.

Any ideas / suggestions gratefully received!

Thanks.