I have 8 saved windows at the moment – occasionally I move a tab from the one I'm viewing to another one (which is often the saved window that's open on another Orion running on another machine).
Doing this will routinely crash the copy of Orion which has that destination window open. When that window is reopened, it'll open with an older state, so tabs you'd closed will now be open – hopefully that's a useful pointer ...
When saved windows were introduced in Safari, I experienced similar bugginess (the tab that's been moved will have the title of another tab, so there'll be two tabs with identical titles, that sort of thing), so I doubt this is Orion's fault, but representative of an underlying flaw in the implementation.
Tabs being moved shouldn't crash the destination Orion
0.99.127.3-beta (WebKit 619.1.1), macOS 14.5 (23F79)
Sonoma (14)