Could you confirm whether the mentioned issue is related to RadControls for ASP.NET AJAX? For example you can remove all the RadControls from your page and if the issue still occurs then it is not related to RadControls.
If that is the case I can suggest that you open a thread in the respective forum (for example the forum of asp.net). If the issue is reproducible only when the RadControls are on board I can suggest that elaborate more into the steps of reproducing it.
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