I recently started a survival world and finding a village somewhat near my spawn point creates an underground village near the place. I gave them jobs and a house with beds. they bred and soon I had my own larger village. I save the game and the next day when I entered my villagers they had disappeared, I thought it was a bug so I used villagers from the creative to make my village again and I made myself an iron farm, when I returned from my explorations the villagers disappeared again . Create another world and the same happens as the previous one. The same thing happens with the animals on my farm. I've even tagged them and they still disappear