While bulding ontop of an existing village, I realised that some of the villagers were stuck in their houses. After some experementation I discovered that carpet was the key to this bug. When there is a door with carpet infront or behind, it prevents the villagers nav-system from allowing it throught. As if the carpet was a full block. Please resolve this issue, it's not game breaking, but it's annoying to have to remove a perfect carpet patteren.