I have searched everywhere for this and cannot for the life of me find a solution for this on bedrock. Why has this gone unnoticed??? Even if perhaps this is a duplicate, Why has this not been fixed either way? Me and friend have a private world that we play on regularly. We have a village and lots of animals. Sometimes when we log in to play, on random occasions, we have our village almost or completely void of villagers. Then we go and try to breed more animals like cows, and we find only one or two in a massive pen which we left over a dozen or more. We have wasted so many resources on curing villagers. Spawning and despawning is a core mechanic in basic Minecraft, so don't put this on the back burner in favor of adding more features. This bug has been around for a very long time. 

You guys need to revamp the entire spawning and de-spawning system. It should match up with Java Edition. Mob Spawners still dont work either. Fix it.