I'm having this issue in Britchester.
I replaced Briny Dorm with another one from the gallery and the lot loaded in, but the base of the building was gone.
The lot just floats in the air with an empty lot below it.
I deleted it and tried another, and the new lot also floated in the air with the base of the tower missing, however the doors and windows snapped to the ground instead of the lot multiple stories above it.
Super weird, closed the game re opened it and the tower is just gone, looks particularly stupid as the tower next to it has the bridge that connects to nothing.
