Can't replace townies

I used to edit the random townies - e.g. DJs or baristas, or replace them by my own Sims - in that case, I'd choose a Sim from my library, and see the standard 'Merge' or 'Replace' option. They still remained townies, though, most of them 'other households' or 'not in the world'. But when I entered bar or a gym, there was a bigger chance that my Sim would meet one of them, rather than a new randomized townie.

I hadn't updated the game for about ten days and just played offline.

Until yesterday, everything went fine. Then suddenly something changed. If I try to replace them, 'Merge' and 'Replace' choices are missing, I can only download the Sim and manually delete the other one. And then I'm taken to the world picking screen and I have to give them a lot, and turning them into played Sims! I tried removing all mods, deleting cache, repairing the game, I even updated it (and didn't put my mods back yet). Nothing works.

Without the option to edit Sims the game's practically unplayable for me, so... help??? What could be causing this?