Unfortunately I am not able to reproduce your issue, and we don't have any record of such problems in our beta releases of Sitefinity 4.0.
Can you give us more details on the steps you are taking in order to reproduce the problem? Moreover what is the browser you are using? It seems like a problem with our RadEditor that we have to further investigate.
Thank you for your collaboration and let me know if you have any issues using our Beta version.
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