Occasionally, while renovating my village, I've found that often, villagers stand outside the house with their claimed bed in it, right on the other side of the wall from the bed, even if the door is less than 5 blocks away and easily accessible (ground level, normal doors, etc.) This causes them to declaim the bed and have no bed to sleep in, making it difficult to expand the village or find villagers as they switch beds whenever they can't claim the one they used to have.