Can you confirm the Core.js file is included in the beginning of the script you have combined and that it is updated with the latest version from our end?
What you can try is to reference it from the assembly to makes sure it is up to date (because all control rely on it) and add it as a script reference at the beginning of the Scrips section:
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.Core.js" />
This next one is the jQuery we bring in case core.js does not suffice by itself.
<asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.jQuery.js" />
Also, make sure that your browser is not using a cached version, because static files tend to be cached. You can clean the browser cache and the ASP cache as well.
I would also like to point out that when EnableScriptCombine property of the RadScriptManager is set to true, all the script files registered on the page from our controls will be combined into a single webresource request. Its URL will be the same for the given script combination until the app pool is recycled, which allows for good caching. The scripts CDN is also a good option if you want to have the needed scripts cached. Taking either of these approaches will reduce the work you have to do to combine scripts and is also likely to yield a smaller request size because irrelevant scripts will not be included.
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