Passive Tamed Mobs despawning

In 3 separate worlds on two Xbox 1x consoles we have lost(in my husband's world) all farm animals, 3 dogs all horses, donkeys, mules & all the gear on them. In my worlds the loss was 2 donkeys, 3 mules, & all the gear on them. I can't find anything recent about this bug other than "use a name tag or it can happen". Some WERE named and they were in solid pens or tied up properly. They just disappeared.