Recently, my Danelectro has developed what I call "acoustic distortion" while playing power chords with 6th string roots. I mean, it sounds exactly like the distortion on my amp if you listen closely. It kind of sounds like a piece of metal is moving about or is a bit loose, vibrating with the strings, but I don't know what. I checked the screws, the jack, the bridge, everything. Anyone have any idea what it is?