The image fully explains the bug, I suppose. Farmlands spawn inside a house, also breaking the bottom part of the door. The upper part still works normally and doesn't even try to "repair" the door. In my opinion, it should be a thing: for example, there could be a tag for blocks that are more than 1 block in size, that states whether any part of the complex block should "repair" itself if at least one other part of it was broken.

Seed: -6167490019935187174. Coordinates: 353 85 175.