Villagers and Other Creatures Disappearing

For the past several months, every time I log into this particular game hosted by my younger brother, Villagers are disappearing from our home base village.  They were named by Nametags and constrained by walls, so they could not reach the roaming distance needed to despawn.  The whole village is well lit, so nothing can spawn within, and we conduct night patrols often.  Also, the walls are tall enough that nothing can climb over or shoot over them.  I've lost track of how many Villagers we've lost.  And it's not just Villagers.  Whole Bee Nests have been found empty; tamed Foxes and tamed Wolves, also named, have vanished; and even tamed Horses with Horse Armor and Saddles, also named, have all vanished from their pens.  This seems to be an ongoing issue, as like I said, it's been happening for months.  And not just on this one server/game; on several such servers/games I play on.