при просмотре на айфоне видеофон с градиентом ведёт себя некорректно

window.addEventListener('DOMContentLoaded', () => {
    const menu = document.querySelector('.nav-menu'),
    menuItem = document.querySelectorAll('.nav-menu__button'),
    hamburger = document.querySelector('.hamburger');

    hamburger.addEventListener('click', () => {
        hamburger.classList.toggle('hamburger_active');
        menu.classList.toggle('nav-menu_active');
    });

    menuItem.forEach(item => {
        item.addEventListener('click', () => {
            hamburger.classList.toggle('hamburger_active');
            menu.classList.toggle('nav-menu_active');
        })
    })
})

html {
    font-size: 62.5%;
    }

.container {
    height: 100%;
    margin: 0 auto;
    
    background-color: #e0dddd;
    
    }
.bg-video {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -4;
    object-fit: cover;
    clip-path: polygon(0 0,100% 0, 100% 55%, 0 85%);
    }
.bg-gradient {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    background: black;
    opacity: 0.5;
    clip-path: polygon(0 0,100% 0, 100% 55%, 0 85%);
    }

.nav-menu {
    position: fixed;
    display: flex;
    flex-wrap: wrap;
    align-items: end;
    -webkit-tap-highlight-color: transparent; 
    min-height: 21rem;
    width: 100%;
    z-index: 7;
    transition: 1s all;
    flex-direction: column;
    justify-content: space-evenly;
    top: 100vh;
    right: 0;
    top: 100vh;
    }
.nav-menu_active {
    top: 25vh;
    }
.hamburger {
    width: 5rem;
    height: 5rem;
    position: fixed;
    top: 3rem;
    left: 85%;
    z-index: 11;
    cursor: pointer;
    -webkit-tap-highlight-color: transparent; 
    }
    
.hamburger__span {
     border: .1rem white solid;
     border-radius: 10rem;
     height: .6rem;
     width: 4rem;
     display: block;
     background: black;
     -webkit-tap-highlight-color: transparent; 
     transition: 1s all;
     backface-visibility: hidden;
     }
     
.hamburger:not(:last-child) {
     margin-bottom: .5rem;
     }
.hamburger_active .hamburger__span {
      -webkit-tap-highlight-color: transparent;
      margin-bottom: -2px;
      }
.hamburger_active .hamburger__span:nth-last-child(1) {
      transform: translateY(2px) rotate(-45deg);
      }
.hamburger_active .hamburger__span:nth-last-child(2) {
      display: none;
      }
.hamburger_active .hamburger__span:nth-last-child(3){
      transform: translateY(4px) rotate(45deg);
      }
.nav-menu__button {
     margin-right: calc( 50vw - 7.5rem );
     margin-left: calc( 50vw - 7.5rem );
     background: $gradient-for-button;
     color: black;
     text-decoration: none;
     padding: 1rem;
     border: .2rem black solid;
     border-radius: 1rem;
     -webkit-tap-highlight-color: transparent; 
     width: 17rem;
     height: 4rem;
     box-shadow: 0rem .5rem .5rem black;
     font-family: 'Robot-light', 'Robot-bobot', 'sans-serif';
     font-size: 1.6rem;
     text-align: center;
     letter-spacing: .2rem;
     text-transform: uppercase;
     }

<div class="hamburger">
            <span class="hamburger__span"></span>
            <span class="hamburger__span"></span>
            <span class="hamburger__span"></span>
        </div>

<nav id="nav" class="main-section__nav nav-menu">
     <a class="nav-menu__button" href="about-me.html">обо мне</a>
     <a class="nav-menu__button" href="publication.html">публикации</a>
     <a class="nav-menu__button" href="master-class.html">моя работа</a>
     <a class="nav-menu__button" href="about-me.html#123" >связаться</a>
 </nav>
 
<div class="container container__main">
            <div class="bg-gradient"></div>
  <video class="bg-video" autoplay loop muted> 
      <source src="img/backround-video.webm"> 
      <source src="img/backround-video.mp4"> 
  </video>
</div>