I didnt have it before. Maybe the rotor or the rim are not straight? Its really annoying sound.
You only hear this when rolling the scooter around...or do you hear it when you are riding the scooter?
Many of us hear some brake drag when rolling most scooters around in the garage.
Use a camera or your cell phone and take a photo alongside your muffler/wheel rim to see the amount of friction material you have remaining on your disc brake pad.
Does the rear brake pulse when applied at low speed?
Have you tried giving the scooter a really firm stop a few times to clean off your rear pads?
None of this matters unless you give us some kind of response.
Stig