Mine only charges with something plugged in the stereo jack, too, and only with the wire hanging in a certain direction. I broke my original charger, so I haven't been gentle with it, obviously.

The charging is a little janky, in my experience. I've had about every flat battery issue, since the device sometimes just stops charging, mid-cycle. I wish they had a locking mechanism between the cable and device, or at least a more firm fit.