This seems to be a common problem, I'm guessing you checked this on either chrome or safari? One possible workaround is by adding transform code into your element's css that has the background-fixed property.
#element{
background-image: url(https://images.unsplash.com/photo-1495578942200-c5f5d2137def?ixlib=rb-1.2.1&ixid=MXwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHw%3D&auto=format&fit=crop&w=1354&q=80);
color: #fff;
width: 100%;
height: 600px;
position: relative;
display: block;
background-size: cover;
background-position: center;
background-repeat: no-repeat;
background-attachment: fixed;
transform: translate3d(0,0,0);
-webkit-transform: translate3d(0,0,0);
}
Working js fiddle: https://jsfiddle.net/Vaulient/f5zy2udt/2/