HI i see in the video your using a black usb lead did this come with beatstep ? as mine are white. also do you have a way to plug beatstep into a usb power socket other than the pc ,say like an apple usb charger. to see if the double notes are still there , you must use the correct type of usb lead for connection to your pc and it could cause problems otherwise .
plugging into your pc could be a driver issue if you have not tried powering it from somewhere else.
let me know how you get on