JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jqueryui/1.11.2/jquery-ui.min.js"></script>
<link rel="stylesheet" href="https://ajax.googleapis.com/ajax/libs/jqueryui/1.11.2/themes/smoothness/jquery-ui.css">
<h2>ui.draggable + ui.sortable stacking context issue</h2>
<h3>(demonstrating regression in 1.11.2)</h3>
<p>Steps to reproduce:
    <ol>
        <li>Pick up the Thing (draggable)</li>
        <li>Drag it over the red box (sortable) - don't drop yet!</li>
        <li>Drag it out of the red box to the empty space below</li>
        <li>You can't! Cloned helper is removed, and the draggable item is now stuck inside the sortable container</li>
    </ol>
</p>

<div class="box pickbox">
    <div class="thing">
        Thing
    </div>
</div>

<div class="box dropbox">
</div>

CSS

.box {
    height: 200px;
    width: 200px;
}

.pickbox {
    border: 1px solid black;
    position: fixed;
    left: 0;
}

.dropbox {
    border: 1px solid red;
    position: fixed;
    left: 300px;
}

.thing {
    height: 50px;
    width: 50px;
    border: 1px solid steelblue;
    background: steelblue;
    color: white;
    text-align: center;
    
}

JavaScript

$(".dropbox").sortable({
});

$(".thing").draggable({
    connectToSortable: ".dropbox",
    helper: "clone"
});