A Prevented Area in Single Player

Put the summary of the bug you're having here
It prevented any acess to a area in single player.
What I expected to happen was...:
Describe what you thought should happen here
I thought it was an open area but it stopped me from entering.
What actually happened was...:
I was mining and I saw this open area. So I went inside and it won't let me in.

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