Community lots are completely empty

I've been able to "fix" the issue in my save by going into build mode when I arrive at a deserted lot - this seems to somehow reset the lot and when I go back to live mode the correct sims start spawning. So far it's worked in all the lots I've had issues with. Bars seem to be the most affected in my save, though it's also happened at cafes (some but not all). It is a very old and bloated save file so I wonder if this might be yet another strange memory issue... But it definitely started with the pre-AA patch.