I just hit this today. Finished Easy Broodmother singleplayer and then spent the next ten ish hours building my base and taking great effort to tame some nice Dinos like Rex and Therizino and went to save it. Quit out to check what mods where available and then reloaded and it went back to right before the Broodmother. The hell? Keeps doing it.
I had been able to overlook a lot of the stupid decisions, bad UI and janky performance on my Series X because it ran reliably. No crashes or anything. Now I can't do anything. Great game guys.