Animals dissapearing from the world

hello i am playing With my friend on minecraft bedrock world (newsy uptade) clifs and something world and if i tame some dog and rejoin the world they would disappear  if i make a villager from zombie villager and put em in a cage and make some trades they would disappear if i lesve and join and if i put some animals in cage which i reproduce for food and rejoin the world they would disappear pls help