Just move the entire modal outside of the rest of your code, to the very bottom. It doesn’t need to be nested in any other element, other than the body.
<body>
<!-- All other HTML -->
<div>
...
</div>
<!-- Modal -->
<div class="modal fade" id="myModal">
...
</div>
</body>
They hint at this solution in the documentation.
Modal Markup Placement
Always try to place a modal’s HTML code in a top-level position in your document to avoid other components
affecting the modal’s appearance and/or functionality.