Broken doors in a village

Just visited a village and found an abandoned house with not passable doors. They appear broken (see pic) and the dark area under acts strange, you can't move on it.
When saved/reopened the world the doors disappeared but the dark area persisted however this time you'd be able to move through. Only by destroying the cobblestone at the entrance took the darkness away.

There was second abandoned house in the same village with the same symptoms.