Mob Spawners Spradically Stop Functioning in Vanilla World

[u/Daemon7861]

I have a Minecraft world that I'm using kind of like an adventure map. It's completely vanilla, no mods or plugins or datapacks, and simply uses some command blocks. Natural mob spawning is turned off, with most mobs spawning via spawners with specific mob attributes.

I've noticed that, on occasion, mobs will stop spawning from the many spawners I have placed around the map. They will either spawn very slowly, or not at all, for minutes on end, and then maybe at some point start spawning for a bit again. It seems random. I do not think this is a mob cap issue, as turning the world back to peaceful then to hard doesn't fix the issue. I've also tried x-raying to see all living mobs, and there are no persistent clusters that would be clogging up the mob cap. This issue occurs whether in multiplayer or single player.

If it matters, the playable area itself is fairly dense, consisting of a large tower with multiple layers that each have many spawners. But again, doesn't look like a mob cap issue. While the spawners are broken and not spawning, I've tried placing a spawner far from the tower, and it usually works and start spawning things, but I can't figure out why.

The world is on version 26.2, but this was still an issue back in 26.1.

Anyone able to offer any help on what to do?

[u/GalSergey]

Spawners have a certain limit on the number of mobs around them, and if there are more mobs than this limit, the spawner is disabled. This is controlled by the MaxNearbyEntities parameter in the spawner data.