This is not a known issue and I suggest you test how our demos behave: http://demos.telerik.com/aspnet-ajax/editor/examples/trackchanges/defaultcs.aspx. You should then compare your setup with the demo setup in order to find the difference that causes the issue. For example, it is possible that some CSS from the site is interfering with the editor content.
As for the duplicated buttons—I advise you review the following article that explains how to define the buttons you want on the toolbar so you can ensure they are not declared multiple times: http://docs.telerik.com/devtools/aspnet-ajax/controls/editor/functionality/toolbars/buttons/add-standard-buttons.
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