If the unit is being overloaded with a load that is near the max limit, that can cause the axle to bend. You may also just have something stuck in the wheels or motor area by the axle. Did you check to see if there is any debris under the frame? If there is no debris, you may need to have a technician check the axle and motor for damage. You can also try spraying a lubricant such as WD-40 on the bearing. Oftentimes, the bearings get dirty and cause the scooter to make noise when it’s moving.