Yeah, I have been observing the same weird tab behaviour. I also work with tab groups and it seems something gets stuck inside a group when every tab is closed. I also see closed "ghost" tabs that are shown to me when I open a new one. Upon loading, of course, the "ghost tab" vanishes and the new tab gets correctly loaded. When closing this new tab, the "ghost tab" comes up again.
Orion 1.0.6 (145), WebKit 624.1.7
MacOS 26.4