[1.12.2] Adding another biome to custom dimension

[The_SlayerMC]

Hi, ive almost been successful with this

Here

 

 

But im not sure at all why this doesnt want to spawn properly, and sometimes where the unrendered blocks are it still says the other biome even though the world generator has placed the blocks according to the biome top block

 

Chunk Provider

Biome Provider

World Provider

Ive gone through the vanilla code and i cant seem to find a fix