Hi I have a similar issue with android auto going off. I've updated my phone and updated to the latest AA version but no resolve. I've bought approved usb cables to ensure an excellent connection. I've been informed by Audi UK that it might be a MMI software update issue but Audi UK haven't stated that it will 100% fix this issue. Apparently no other business can update the MMI system other than Audi. They want £130 just to plugin with no guarantee of the fix.
Good luck
Bob