I have a 2011 Ford Fusion Sport with Nav. when I connect my iPhone 6 via USB, I open my Spotify App to play my music after I select a song if I lock my phone or leave the app, after about a minute and a half into the first song the app crashes and closes out. I found out if I leave the app open and the device unlocked throughout the first song then everything is fine and I can lock it and what not. What is causing this and how can I fix it? It's very frustrating when I pay for premium and all my other music apps work perfectly.