“Cannot unregister UpdatePanel with ID ‘xxx’ since it was not registered with the ScriptManager… ” in RadGrid while editing record

Let me cut to the chase. My scenario is as follows: I have custom added fields to filter the RadGrid and filtering works perfectly. The problem comes when I want to edit record using EditForm inside RadGrid. It used to work fine, but then I had some problems with selecting the right row (I was always getting the wrong row selected) so this is what I did to fix it.