ios image filter blur css has a boundary line

This boundary line is not permanent. It seems more like an ios rendering bug. Is there any workaround with css?

  • looks bad:

enter image description here

  • make some actions, like switching the app into background and reopen it, and the bug disappears
    enter image description here

the css of blurred background image is

.img {
    position: absolute;
    top: 0;
    left: 0;
    width: 80%;
    height: 100%;
    object-fit: cover;
    filter: blur(20px);
    opacity: 0.1;
}