This is a strange one...the standard stereo in my wife's A5 doesn't turn onto a source (e.g. radio) 99% of the time even when it is switched off listening to the radio. The screen powers up and shows the MMI logo, but you have to press a source button to hear music. Perhaps 1 time in a 100 it will come on.....we all comment on it when it does!

Audi have looked at it and can't find anything, they even replaced the head unit. I've scanned the car with VCDS and found no codes.

Any suggestions?