I built the neather core and activated it and it worked fine then I destroyed where it was and built a new one in the same spot and what happened when I activated it again the neather core changed color like it's supposed to but the gobblestone and gold did not. It made the obsidian surrounding like it should but nothing else happened. None of the pig men spawned none of the drops spawned and after sitting in there for 5 mins the neather core didn't power down and the obsidian walls didnt break so I could get out