We are sorry for the inconvenience. This indeed is an issue that appears because RadRichTextBox "steals" the focus when the button is pressed, which leads to lost button click event, when button's ClickMode
A workaround would be to set button's ClickMode
Fortunately we resolved this issue right away and the fix will be available in the upcoming beta release in a couple of weeks. Let us know whether this helps.
the Telerik team
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