The scripts of the controls are not combined in a single request, when the web.config key Telerik.ScriptManager.TelerikCdn.CombinedResource has value Enabled:

Steps to reproduce
1. Ad the following configuration in the web config and open a page containing RadControl.

<appSettings>
    <add key="Telerik.ScriptManager.TelerikCdn" value="Enabled"/>
    <add key="Telerik.ScriptManager.TelerikCdn.CombinedResource" value="Enabled" />
  </appSettings>

Result: The scripts are not combined.


Workaround:

Enable the script combining in the ScriptManager declaration:

    <telerik:RadStyleSheetManager runat="server">
        <CdnSettings CombinedResource="Enabled" TelerikCdn="Enabled" />
    </telerik:RadStyleSheetManager>

When it is not possible to load scripts/styles from CDN, the scripts and styles should be loaded from embedded resources.

Please monitor this item as it was the original and has more votes: https://feedback.telerik.com/Project/108/Feedback/Details/119156-add-cdn-fallback-to-local-support-added-to-radscriptmanager-radstylesheetmanager