I have several sites that are missing these files. This is causing errors on the browser console. Also, I think this is causing errors with my host and our WP REST API, but I digress.
/wp-content/plugins/meta-box-aio/vendor/meta-box/meta-box-builder/assets/js/popper.min.js.map
It's a JavaScript Source Map, and is meant to be included with popper.min.js, for the browser.
I've been trying to track down errors with my host, WP Engine, and this bug is one we're trying to knock out.