"Despawning" Villagers

I am playing on my own, private world on version 1.17.2 on bedrock. Before the Caves and Cliffs update, I lived next to a village. One day, all the villagers vanished. I went to visit the village, and they were just all gone. I looked it up and found that villagers sometimes leave I think? So I didn't do anything. I now have Caves and Cliffs. Yesterday, I traveled pretty far and brought two villagers to my home, after the update was already installed. I built them their own home right near mine with plenty of beds and job stations. The only thing about the home was that the roof was not complete, but I read that spiders and phantoms don't attack villagers. Today, when I went to check on my villagers, they all disappeared again. None of them were there, there's no way to get out, and there was no zombies in their place. They just vanished. What's causing this/how can I fix it?