If you haven't recently hit any massive pot-holes - with a panel knocked loose - front fender, for example? If not
it is likely nothing serious.
Scooters can make all kinds of noises when rolled backwards.....CVT making a noise being rolled in reverse, brake pads or shoes rubbing - especially when bars turned sharply.
IF it makes noises when rolled forward - that is a different situation.
Certainly a visit to your dealer is warranted if it continues to bother you - in the mean time don't ride it in reverse.
Stig