Neighboring Houses show as Default/Empty

I turned Camp Gibbi Gibbi into an archery and meditation custom retreat, then replaced the playground with a forest that had some items from other packs on it, including a hot spring from Komorebi and a couple Enchanted by Nature items. This completely blew up every lot I'd ever made, which was a lot of lots, I've spent years now editing neighborhoods into custom layouts. Everything went back to base game default. All sims still lived where they lived, it's just the lots themselves completely reverted to default. Unfortunately I no longer have the ruined save files though, today by sheer (and lucky) coincidence I actually bothered to back up my save for the first time, so when everything blew up I just reverted back to the backup. I could probably break it again if necessary, though. I only realized I should probably report this when discussing it with a friend later.