Nether biomes appear in the overworld

[Colegalapaz]

Nether biomes from the mod appear in the overworld. I added the mod on an already generated world and deleted the DIM-1 folder to reset the nether, but the biomes from this mod just happen to generate in the overworld, well, not generate, but now some old biomes count as nether biomes and mobs from those biomes appear, like fireflies and fire jellyfishes, you can also see a red fog like in the nether, you can still place water down.

[Groupix05]

It may be a Minecraft problem ,this one : MC-202036 ,if you don't have any mod that fixes this error .