You need to check whether the handles and tubing are connected tightly. 2. The bands should be used between 0°C - 40°C ,because pulling of tubing is not affected in these tempreture. 3.Cannot have friction with hard objects when you use the bands , bands would better strethced up to 3 times of its origial length. 4.If bands are out in the air for long time ,the surface of bands will turn out to be white.But this is  normal case , it won't change the function of products.Just use wet towel to clean the surface.