I have 2012 Q5 (no nav) and I loaded a 4GB SD card with songs from iTunes. When I tried to play them back I discovered that only a few of them, non consecutive, could be played. I erased the card and re-wrote the songs through another PC, using the same iTunes library (all legal). When I tried to play the songs I discovered that EXACTLY THE SAME songs could be played and not the others. I repeated the procedure with the same results. It drives me crazy. Any advise please?