I have a TuneBase FM and an iPhone 4. The sound quality is pretty good, if I crank the car stereo volume. The problem i have been having lately is that the volume suddenly drops to like 1/4 for a second or so at random times, for no apparent reason. I'm listening to music, and zap, almost silence, then it comes back. Extremely annoying. I can actually see the volume bar go down on the screen... so it's actually lowering the phone. The other problem I have, which I can work around using the on-screen controls, is that the "multi-function button" rarely works. I can click in several times and maybe one click will register. I cannot reliably answer phone, and forget using it to skip tracks. Sometimes it DOES work, though... just not reliably. Anyone else see this, have any ideas?