Disapearing entities

A couple of entities have disappeared around my Base. I breed villagers, left for a second to get more bread then came back and parents were gone, again I left for a second and the children disappeared too (definately weren't killed), this also happened to my happy ghast and named zombie, it is incredibly annoying as all of them took a long time to get in survival (I spent ages getting ghast tears, name tags and dealing with annoying villagers and transporting them)