There may be hair or debris entangled in the base of your propeller. To remove the debris, use the little silver lever (that comes with the drone kit) to pop off the propeller. Clean out the base (you may need some tweezers), and then just pop the propeller back into place. If that doesn't work, or if you know there isn't any debris, you may need to replace the propeller altogether. Here's the link for the manufacturer's replacement parts: http://www.protocolny.com/spareparts/drone-spare-parts/vento-wifitm.html