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I have this huge gap in my world. I was just starting to get things going with the FTB mod so please tell me this is easy to fix.
When I enter it I can move forward very slowly. I did not move in all the way but just a bit with SHIFT and took me some time to get out of it. I cannot build in it either. For further experimentation, I need to bring my Efficiency IV, Unbreakable III, and Fortune II diamond pickaxe to safety first, which is another reason I want this world fixed.