Villagers with name tag and job, disappearing in hardcore world

In my hardcore world, I have been turning my spawn island into a huge village with villagers with all different jobs.  First, I had a villager (name tagged) that was a librarian disappear randomly and I just traded with him about 10 mins before he did.  The second time was my villager (name tagged) who was a farmer who I have had for a while now, just disappear randomly.  I am not sure why they keep disappearing because they are also trapped and cannot be killed whatsoever.  

If this issue can please be fixed, I would love all my villagers.  But right now, I am constantly on edge that they will disappear every single time I look away.  Not to mention, it wastes my name tags and those are hard to get.