Disappearing tunnels in main world. Started to create my underground base and dug numerous tunnels during the process. I cooked the stone to make bricks. Traveled to the Nether and started my Nether Base. At this point I logged out of the game. Logged in the next day to find that all my main underground area was filled back in with the exception of a small area where my furnaces were stationed. I ran to the Nether to check on my work there. My work on my Nether base was intact.

Was kind of nice to re-mine the diamonds.

BTW: Why can I not find my version here? My version on the Xbox page says v1.2.1? Makes reporting bugs kind of difficult.