Your observations are absolutely correct and this is a known issue. We have already fixed that problem and a fix will be included in one of our upcoming internal builds or service pack release. Could you please clarify whether you are facing that issue when you quickly click on the expand icon before the previous post-back is not done yet? If you are reproducing that issue under different circumstances, please share with us some steps or a video to replicate that problem.
the Telerik team
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