Loading the same module several times is not useful because the code is already present in the page and can be exploited by the browser. A module declared several times therefore unnecessarily increases the weight of the page, as well as the interpretation required by the browser and delays its loading.
The detection of duplicate modules is based on their "source Maps" file (additional folder that allows debugging the code). Usually these files are filled by the CDN (Content Delivery Network) within the script itself with the instruction "//# sourceMappingURL=...".
For example, the Bootstrap framework is loaded twice despite different names :
<script src="/js/bootstrap.bundle.js"></script> <script src="/js/bootstrap.js"></script>
In order to correct it, you have to remove of one of the two statements :