New information that might help isolate the problem.
I've been getting around the 533 issue by saving my lot to the library and bulldozing the current lot. I'd then place it back into the game and save as normal. This time it didn't work, because it was the lot itself that was bugged/glitched. I deleted everything manually, and when I tried to bulldoze the lot the game said the object couldn't be found.
I used the club feature to gather the entire family on another lot, and when they weren't at home I clicked on manage worlds and tried to replace the lot from there. Again, I received the message "Object not found." It was referring to lot itself, and not the building or any objects found on it. I returned to my active family and kept them on the community lot while I saved the game. It bypassed the 533 error, but I still had the issue with the lot. A game restart fixed whatever caused the issue, and I could place the home from my library without my sims losing any progress they made before the glitch.
Could the problem be in the world files, or wherever the empty lot files are located?