I'm afraid it is difficult to figure out your exact scenario by the provided information so far. Assuming that you want to make conditional updating, you can configure the AjaxSettings of the manager according to your requirement:
Menu updates => Items
Items update => Grid
Therefore, the AJAX request and the response from the server shouldn't include the Items when the grid is updated.
Hope this helps. If you have different requirements or further instructions, please elaborate on your specific scenario and open a support ticket to send us a very basic runnable web site demonstrating the problematic behavior.
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