I play on the FTB server often and last night i built a huge building. Then i saved and went to sleep. But, This morning when i got on a chunk inside of my building was completely gone. But the game still sees the blocks are there but i cant see them and if i walk on it i start talking damage. I ve tried logging out and in a couple times. Ive also copied and pasted the world several times. Can anyone tell me how to fix it?