i spent 4 hours troubleshooting this.

i realized my biomes were shifted, what's that? well, i was living on a BoP wetland and suddenly, when i realized desert zombies were spawning, i realized the biome was a wasteland. so i checkedd and realized that when using this mod, the biomes get shifted around, messing up new world gen and current biomes. you should probably check this. note this was on an already generated world.

upon continuing my investigation i have realized its not this mod only, it appears to be the 49th mod installed.