Hey all, I just sent my sim to China and am not interested in having them purchase an existing empty home (I usually buy an empty lot and build one myself anyway), so I figured I'd change them to "Non-Player Sims Only" so that local families could move into them. The problem is that while the game does let me do that in Edit Town, if I save and quit the game and reload the save, the houses are back to being listed as "Ownable Lot" (i.e. the type that can be purchased by the active sim/family).

Is this a bug? Has anybody experienced this before and knows how to make the lots stay as NPSOs?

It is indeed a bug. Change the lot(s) to Community-anything (No Visitors Allowed will do) first, then change them to Residential-Regular or whatever other designation, and the new one should stick.

Thank you!