This is probably listed on here somewhere but I only found this out today. I have music on the sdcard in the nav and I also have music on my iPhone. But for some reason when I play through the iPhone source I can’t skip tracks with either the wheel or the unit itself. It turns out you need to create a folder in the garmin unit and name it mp3, you don’t have to put any music in it, do this and for some reason the wheel and nav then lets you control the tracks, easy fix.