I can also try putting the same build in a different lot with another test sim just to see if those stairs normally work, if my original test sim is still stuck on her accursed lot watching the world burn around her.
@crinrict So the third time was the charm. When I returned to the save, it started me back in the middle of the Cursed Book event like I was stuck in the movie "Groundhog Day," so I tried teleporting my sim to the upstairs room where the book was, and she was able to destroy it once she was up there. The stairs were still broken (not certain yet if they were downloaded that way, but it seems likely), so I had to demolish and rebuild them. There were a few other glitches after that, but they seemed like the normal garden-variety sort of annoying glitches commonplace in Sims 4, nothing that significantly affected gameplay.
A special service of thanksgiving will be offered up at St. Crinrict's Chapel, Newcrest, at noon tomorrow. No actual llamas will be harmed in the token sacrifice.
