Yes, there's an issue where if the ground/power pins have a poor contact (due to a bad/dirty cable or whatnot), you end up up with a short on the pin which creates tiny shocks that leave a carbon discharge, and making it drop the charge. Your phone will now create carbon discharge on any new cable, spreading the "disease" to other iOS device. Look around at any "public" lightning cable for black spots on one of the middle pins.