Currently, the GetDesignerResource endpoint of the Web Report Designer service is case-insensitive, which can lead to issues if the URL is made lowercase at some point, such as by a URL rewrite rule, or similar scenarios.
For example, the following reference to the Web Report Designer script will load return the file:
<script src="api/reportdesigner/designerresources/js/webReportDesigner"></script>But if lowercase is used, for example, like this:
<script src="api/reportdesigner/designerresources/js/webreportdesigner"></script>The request will return a 404(Not Found) response.