After something is built the game loses the data at random and reverts back to the original landscape. This occurs when the area is reloaded by walking away and coming back or exiting the game and coming back. The affected area seems to be about 16x16. The chunk of area affected is from sky limit to bedrock reverting the entire chunk back to the original data before it was ever modified by a player. For example, I built a structure roughly 50x50 blocks and the middle of it just disappeared and reverted back to the original landscape while the walls of the structure remain. This seems to occur at random. This does not occur every time the game is loaded. Roughly happening about once every couple of hours of game play. The issue is not revolving around any one single player on the realm.