Nether completely changed, and the screen is super grainy.

Put the summary of the bug you're having here

What I expected to happen was...:

Go to the nether and go through a portal that leads somewhere else.
What actually happened was...:

Went to the nether and my other portals were gone and I was in a whole different biome then usual.
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...
3. ...