Minecraft: Why do my villages / villagers die out?

Ch
2

After trying Minecraft again after a long, long time, I came across a real problem that I did not have before:

My villages are dying!

For one thing, my villagers are gradually disappearing - even though I've eliminated all the death traps and even built a city wall around the village. And on the other hand, it is no longer possible for me to break new Villager. In the past it was enough to feed them with bread and to have enough houses (with doors and now also beds).

Although I live in a settlement with at least 10 fully equipped houses, the three remaining inhabitants are no longer willing to mate. Even if I feed them with bread and the hearts appear, another symbol (lightning and clouds?) Intervenes and nothing happens.

Who can help me?

Do

The villagers need houses where they can get in when night falls, mobs are spawned at night, kill villagers or zombies that infect the villagers so that they themselves become zombies

Ro

I think you can despawnen too.