When the FluentPalette.Palette.ScrollBarsMode property is set to Normal, the ScrollViewer scrollbars overlap the content area. This should not happen.
To resolve this, set the ThemeHelper.ScrollBarsMode attached property of the ScrollViewer controls using an implicit style.
<Window.Resources>
<Style TargetType="ScrollViewer">
<Setter Property="helpers:ThemeHelper.ScrollBarsMode" Value="{telerik:FluentResource ResourceKey=ScrollBarsMode}"/>
</Style>
</Window.Resources>