Ideas
I don't know if this is related or not. But I wanted to add my 2 cents here if it's helping the devs with some problem solving. My game starts to stutter whenever the disappearing neighbouring builds/lots bug occurs.
I have a save game I curate for at least 5 years now with many new households and all lots replaced by new ones from the gallery and from other downloads as I am no builder. The first thing I do, when I get my hands on a new pack is to change the builds on those new lots. And as I know about those save corruption bugs, I always keep my eyes sharply on possible hints in the worlds.
One of those hints I noticed is when I am hopping from one lot to another to change the build, is when the game starts stuttering non stop. I then always exit the game without saving as this is the point when my neighbouring lots start to dissappear. I don't know why that is. I just go into a lot, change the build, save and go to the next one. For like 2 - 3 builds it works and then the game starts stuttering. I checked two times when this began what happens in the world and I let a sim of mine travel through different lots and the disappearances occur. I then roll back the save and check those lots again and everything is fine.