Может быть, использовать псевдоэлемент вместо тени?
выглядит иначе.
см. Ниже
html,
body {
margin: 0;
padding: 0;
height: 200vh;
}
.frame {
margin-top: 12rem;
width: 500px;
margin:100px auto;
}
.tile1 {
background-image: radial-gradient(circle at 101.4% 0px, rgba(0, 0, 0, 0) 0, rgb(222, 184, 135, 0) 105px, coral 105px);
height: 300px;
filter: drop-shadow(0 8px 16px rgba(0, 0, 0, 0.5));
}
.tile2 {
position: relative;
background-image: radial-gradient(circle at -1.4% 0px, rgba(0, 0, 0, 0) 0, rgb(222, 184, 135, 0) 105px, coral 105px);
height: 300px;
}
.tile2::after {
content: '';
z-index: -1;
top: 0px;
left: 8px;
filter: blur(16px);
position: absolute;
background-image: radial-gradient(circle at -1.4% 0px, rgba(0, 0, 0, 0) 0, rgb(222, 184, 135, 0) 105px, rgba(0, 0, 0, 1) 105px);
height: 100%;
width: 100%;
}
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8" />
<link rel="stylesheet" href="style.css" />
<title>custom div</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
</head>
<body>
<div class="container-fluid">
<div class="row">
<div class="col-lg-6">
<div class="frame">
<div class="tile1"></div>
</div>
</div>
<div class="col-lg-6">
<div class="frame">
<div class="tile2"></div>
</div>
</div>
</div>
</div>
<script src="https://code.jquery.com/jquery-3.5.0.min.js" integrity="sha256-xNzN2a4ltkB44Mc/Jz3pT4iU1cmeR0FkXs4pru/JxaQ=" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
</body>
</html>