Mobile fixed image background css, image scrolling

I'm making a website for my girlfriends 23rd birthday and she'll mainly be viewing on mobile. The background image is fixed (no issue on desktop) but on mobile, the image scrolls slightly on the bottom, but adjusts itself after scroll. (Video Attached: https://youtu.be/wKnxYXEy0mg)

CSS Below:

body {
   background-image:url(Gold2.jpg);
   display: block;
   background-color: gold;
   background-repeat: no-repeat;
   background-size: cover;
   background-attachment: fixed;
   background-position: center;
   min-height: 500px;
}