my computer when i spwan in a new world some times the biomes mix and looks like the mountains are taken off

Put the summary of the bug you're having here

*What I expected to happen was...:*that the world would look perfectly generated
Describe what you thought should happen hereits was half the world riped off

*What actually happened was...:*i spawn and see that half world is gone
Describe what happened here

Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...