ZAMK14 Sunset Valley is the only world that comes with the base game. When you say other worlds disappear, I think you mean EP-related worlds (e.g. Twinbrook, Bridgeport), but do you also mean other Store worlds or custom worlds? And are the worlds you're installing that trigger the problem Store worlds, or custom worlds, or both; and is it other Store content that triggers the error?
Please also let me know whether the packs you own disappear from the launcher's Expansions & Stuff Packs tab. If they're still present and checked off, but those packs aren't loading in-game, uncheck and re-check the boxes, then try again.
