Sorry, definitely haven't seen anything like this. When you say stutter, is it actually repeating a segment of sound, pausing, or effectively cutting out for a second or two?
Just an initial thought might be some kind of loose harness somewhere. The fact that it's happening on broadcast radio tells me it's not an input issue, that's as basic as it gets. Also, does it happen regardless of whether you are moving or just say in your garage listening?
Another thought would be to try doing a full reset via holding power button and skip forward on the console. Do it twice in a row to be sure. You could also try loading a newer version via online update or cyanlabs (directions all over the place on here).
