Dmscomp8892

So I've had my 2012 rs 7.0 since new and I just noticed that when I'm playing music from my iPod through the USB jack, the radio switches out of USB mode into either cd or tuner when that car is stopped and then shifted into park. I don't remember it doing this before but I figured is see if anyone has any input. The radio has just started working in USB mode since I got the USB 4 error last month. It's the basic pioneer stock radio.