I am attaching an ASP.NET Core solution, where a similar scenario to the one described is demonstrated (Reloading a tab of the Kendo UI TabStrip).
With the above example, the second tab can be reloaded by clicking on the button below the widget. This can be observed in the network tab of the browser - each time the button is clicked, a request is being sent to the remote service to retrieve the contents of the tab. Notice that the content for the tab is returned from a partial view.
Can you test the example and verify that it is working correctly on your end? In case I am missing something, then please modify the solution, so that the issue faced is reproduced and send it back to us for a review.