I guess that this is expected behavior. You are resubmitting the form data and the last operation will be repeated on each refresh. The browser should warn you about that.
The solution is to use AJAX, either wrap the scheduler in an UpdatePanel or use RadAjaxManager, as in the online demos. This should resolve the issue, as the commands will be transferred via asynchronous connections and they will not be resubmitted on refresh.
All the best,
the Telerik team
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