I just had some villagers disappear/despawn on me in the 1.16.0.59 Beta from my iron farm (which is chunk aligned in a single chunk). The villagers were brought in using a spawn egg. After doing hours of testing, unloading the area, and then loading it back up, they were gone.

I do not believe that this is a Duplicate of MCPE-47922, or MCPE-21416 as this happened while being chunk aligned and is happening in the Beta.
Below is a link to the Iron Farm video that I made, you can see in the beginning that the villagers were there and spawning in Golems. After if flew almost 1k blocks away and then back the villagers were gone. https://youtu.be/yfqTRRu3K6w