Improper Villager spawn types (white robed instead of brown robed)

I was traveling around a map when I came upon a randomly generated village. For some reason all of the villagers were librarians (white robed) instead of being the brown robed villagers. There were only two librarian houses in the village, a blacksmith and blacksmith house (that spawned properly), and several other houses that usually spawn brown robed villagers, but instead they spawned white robed villagers. I was originally playing on a customized map, but when I used the standard map generation it was messed up as well (although it did manage to spawn one brown robed villager properly). the seed I was playing on was -845211039965335995 and the co-ordinates of the village were at X=36 Y=102 and z=277. I have generated this world four times and every time it has generated improperly.