Whenever I try to make a nether-themed build in creative in the overworld that involves Piglins, the only way I can find to fix this is turning the random tick speed down to zero. This however causes the piglins to begin teleporting (either that or they're despawing). The same thing happened with baby piglins, and also when the random tick speed was returned to normal. (Edit: They dissapear, and then respawn in the room a while later).

How to reproduce:

1. Create a Flat World in Creative

2. Build a large (12x14?) square enclosure.

3.Turn the Random Tick Speed to Zero

4. Spawn a Piglin and wait a about a minute.

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(I did a have a villager in the room, I'm not sure if that affects it?)