The floating toolbar window does not open when the user toggles to full screen.

You can resolve the issue by incorporating the following script block:

<telerik:RadEditor runat="server" ID="RadEditor1" ToolbarMode="Floating"></telerik:RadEditor>

<script type="text/javascript">
    Telerik.Web.UI.Editor.DefaultToolAdapter.prototype._showToolbarHolder = function (isVisible) {
        var editor = this.get_editor();
        var toolbarEnum = Telerik.Web.UI.EditorToolbarMode;
        if (!isVisible) {
            if (this._toolbarHolder) this._toolbarHolder.hide(); //NEW - Add a check for the toolbar holder
            return;
        }
        
        //Hide if in fullscreen mode and toolbar is ShowOnFocus
        if (editor.isFullScreen() && editor.get_toolbarMode() === Telerik.Web.UI.EditorToolbarMode.ShowOnFocus ) return;

        //Hide previous wrapper and mark yourself as the wrapper
        var wrapper = Telerik.Web.UI.Editor.DefaultToolAdapter._visibleWrapper;

        //Return if you are already visible
        if (wrapper == this && wrapper._toolbarHolder && wrapper._toolbarHolder.isVisible())//NEW - toolbar holder might not be created!
        {
            //Activete it before returning, as it could have been deactivated after showing an editor dialog
            wrapper.get_toolbarHolder().setActive(true);
            return;
        }

        if (wrapper && wrapper._showToolbarHolder) wrapper._showToolbarHolder(false);
        Telerik.Web.UI.Editor.DefaultToolAdapter._visibleWrapper = this;

        //Create the holder in the last possible moment before showing
        this.get_window();

        //Do additional initialization depending on toolbar mode
        this._initNonDefaultToolbarMode();

        //Show toolbar hodler
        this._toolbarHolder.show();

        //IE, ShowOnFocus, PageTop: hide properly the fake toolbar parent here instead _moveToolbarsToEditor
        if ($telerik.isIE) {
            var toolbarMode = editor.get_toolbarMode();
            switch (toolbarMode) {
                case toolbarEnum.ShowOnFocus:
                case toolbarEnum.PageTop:
                    editor.get_TopZone().firstChild.style.display = "none";
                    break;
            }
        }
    };
</script>