Steps to reproduce

1. Create a world without Caves & Cliffs experiements, with seed 648853.
2. /tp 16 80 291
3. Save & quit.
4. Enable Caves & Cliffs experiments in the world settings.
5. Load the world and /tp 16 -43 291.

Expected result

The spawner at 16, -43, 291 has a zombie spinning in it and spawns zombies, and the chests in the dungeon have loot.

Observed result

The spawner at 16, -43, 291 has nothing spinning in it and does not spawn anything, and the chests in the dungeon cannot be opened and drop nothing on breaking.

I found a cave spider spawner inside a mineshaft I lit it with torches to stop them from spawning and left the mineshaft I went back to get some EXP so I removed the torches and the spawner appears as if it's empty it has no mob spinning inside nor does it have the usual flame effects and nothing is spawning from it. When I remove the torches the light level should be enough for them to spawn and there should be a cave spider spinning inside the spawner