Be sure you are using only genuine BISSELL® replacement belts. Belts not made by BISSELL may break continually. If you need replacement belts, please call 1-800-263-2535 and a Consultant will be happy to place an order for you.
Adjust height of vacuum using the height adjustment knob. By raising the base slightly, this should help to ensure the brush is rotating freely.
If the problem persists, please take the machine to a BISSELL Authorized Service Center to have a technician check it.
You can locate one by clicking here: http://www.bissell.com/service-centers/