Check in other browsers.
However …
unless you are hiding stuff from us, that will break autoupdate for this Item.
Meaning that its state will not change in response to commands.
Sitemap button highlighting is derived from Item state.
What group? You mean,if you use a Group widget in your sitemap?
Yes, that’s entirely expected. When you display a set of Items with a Group widget, each one is displayed with a default widget. There is no way to customize any of them for buttons, colour, etc.or even change the order.
If you need something like that, build the sitemap by hand instead using Text { } widget instead of Group widget.