I do have custom content and mods and have had them for ages without this glitch. I did try without and still glitched. It works in Sunset Valley without the glitch. I've spent the last few days, rebuilding my partially created world. I'm going to back it up once the basics are added. I spent yesterday working on the custom school with rabbithole doors and today on the Stadium/Gym also with rabbit hole door. Now I've just started the Science Centre and am looking for the fountain to put in front of it. I think the problem does have to do with that/those books that have become impregnated into my lots somehow. I just can't find the lots to get rid of them.