On my Realm world, we have been transforming zombie villagers into villagers but they have all de-spawned, even if we've given them name tags. There is no way zombies can get to them or for them to die. They have set beds and set workstations but no matter what we do, they always de-spawn after a while even after trading with them as well. It is quite frustrating, especially after finally getting a mending villager just to have it de-spawn after a handful of trades. I am currently on Version 1.16.210 on bedrock (Xbox 1 to be specific)