I'm building this world with around 12 TARDISes but 4 of them have vanished. is this is a bug or something & how do i fix this?

In creative mode I've been unable to place the grandfather clock and ruth TARDISes in update 54; I think this is what he's talking about. When placed they disappear immediately. They don't generate interiors or add to the player's TARDIS id list.