So was playing normally with my wife on bedrock (Xbox series x, split screen) she had corralled some farm animals into a large barn, separated them out, and had bred lots and lots and lots of chickens, sheep, cows and pigs, with the possibility of slaying or shearing them, some time later we realised that it was acting as a mob switch any time we were near the barn, nothing will spawn, no matter what dimension the other person is in, this was confirmed when we decided to kill the chickens and pigs, things started spawning and it was a lightbulb moment.
Tldr: too many farm animals creates mob switch
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Comments 5

How is "can spawn naturally" the same as I bred these extra...

Sheep, for example, can spawn over and over on grass in daylight as you move around the overworld, while armor stands and villagers cannot. Villagers only spawn with the initial generation of villages or igloos, and armor stands are only spawned by players placing them. Sheep have environmental spawning rules, villagers and armor stands do not. All mob types that have environmental spawn rules count toward the global cap based on their type. Individual history makes no difference.
Sheep and passive mobs also have a much lower chance of spawning, their own mob cap and I could understand not spawning any more passive mobs because cap reached, but to outright cause 0 spawns across the board... That's where the logic breaks down.
Considering how long the bug hasn't been updated, is it still an issue in the latest version?
Bedrock Edition has a global cap of 200 spawnable mobs. If 200 mobs that can spawn naturally are loaded then environmental spawning stops. I believe this is working as intended.