I was playing in my world around where I keep my villagers when I had to quit the game. When I later reentered into the world, half of my villagers (2 out of 4 of them) despawned with out a trace. At first I thought they may have died somehow or got loose before I quit, so I respawned them back until I had to quit again. And when I came back into the world, another 2 villagers despawned.

I expected for my villagers to still be in the same place they were when I left the world earlier.

Instead, some of them despawned when I reentered into the world.

Steps to reproduce:

1. Have some villagers near you when you quit the world
2. Quit and reenter into the world many times (To make sure the bug happens)
3. Notice that some of your villagers near you have despawned from your world

 - May be the same with wandering traders and their lama's 

• I saw that others have reported this same bug but they were dismissed because of too little information regarding the bug

I hope all this information helped.