I am playing on xbox one.  In our realm we have problems with villagers disappearing as well as golems we have named.  We even built a big house with metal doors and put a golem inside with the villagers. Still they disappear 1 or 2 at a time. All of our villagers now are cured zombie villagers but they keep disappearing.   Our big house we made for them has lots of light no place for darkness so we dont know why they keep disappearing.