I just bought an official iPhone 6S Apple Dock (space grey) for my iPhone 6 and have it plugged in however I am finding that when I touch the top of it (the flat part behind the actual dock connector which the phone sits on to charge), the dock kind of vibrates?! It's as if I can feel the electric current running through it? I know it is the current because if I then unplug it, I can no longer feel this? At first, I thought it was because I was using a third party lightning connector lead to attach the dock to a usb power outlet but I've also tried the dock with the official Apple lightning connector lead but it does the same thing?! It's not a strong vibration but you can feel something vibrating when you rub your finger back and forth on the flat part of the dock (behind the connector part). The phone charges fine. Do you think I should return it (bought directly from Apple)? Could there be a fault?