[2020] Builiding is not deleted automatically when I change the Area

If you're using Plop the Growables, then this is completely normal and expected behavior because of the mod.

If you're using Disable Zone Check, then that's also completely normal and expected behavior.

If you're using Ploppable RICO and the building(s) in question have RICO settings through the mod, then it's also completely normal and expected.

Those are the 3 mods I can think of, which change building behavior so they don't despawn automatically when you dezone. :)