A test world I was using far long before super flat worlds were even a thing. It is a 1000 x 1000 flat world save download that was made flat by someone on the minecraft forums. Has some sort of corruption where if i were to go to the original edge where the bedrock wall was I get stuck and cannot do anything. Commands don't even work such as teleporting. And If I were to place this map on a server the server would crash and would need a restart every time a player reaches the edge of the map.
I have a solution but i would like to know if it's safe. I can create a new world and move everything over using MCedit. Would moving everything i want to keep cause the same corruption?