R56 weird infotainment issue
 

Not sure if I'm in the right place. I have just purchased a 2009 R56 and there's an issue with the infotainment system. Bit of a strange one. When I turn the ignition on (not starting the car) the infotainment system works fine but as soon as I start the engine I get no sound. I can see on the screen that it's still playing music though. Also the home and page buttons don't work. Turn the engine off and everything works again.

I've checked the fuses and changed them out for new ones and it has a brand new battery. I've been pulling my hair out with this and surfing the forums for hours.

Anybody got any ideas as to what might be causing this.

Thanks in advance for any suggestions