모바일 브라우저에서 '위치: 고정'이 제대로 작동하지 않는 이유는 무엇이며 어떻게 해결할 수 있나요?

<code class="css">.fixed {
  position: fixed;
  top: 0px;
  left: 0px;
  width: 320px;
  height: 50px;
  background: red;
  -webkit-backface-visibility: hidden; /* Most Important */
}</code>

<code class="html"><div class="fixed">
  Hi I m Position Fixed
</div>
<div>
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</div></code>