add a workaround (add 1px margin to the left) to avoid the artifacts when the selection indicator animates
MODIFY
WalletWasabi.Fluent/Controls/NavBarItem.axaml
WalletWasabi.Fluent/Controls/NavBarItem.axaml
Padding="{TemplateBinding Padding}"
VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" />
- <Border Name="SelectionIndicator" />
+ <Border Name="SelectionIndicator" Margin="1,0,0,0" />
</Panel>
</ControlTemplate>
</Setter>

add a workaround (add 1px margin to the left) to avoid the artifacts when the selection indicator animates