Having trouble with the viper mini

This started just yesterday , my viper mini when changing dpi from 800 to 400 at first is ok but after a few movement and swinging around just locks into some lower dpi and you can feel the dpi has dropped for some reason (i only have one dpi set , not stages ik -_-). I think the sensor is messed up , how do i get a replacement? , Any help and direction appreciated.