Old Worlds very buggy!

Hi, when playing in any old world, there seems to be certain regions where the world is corrupted and will crash. However, it only crashes only after you edit something (eg place a block) I tried lighting TNT and it crashed the game and kept on crashing after when I try to enter the world.
Edit: This seems to only affect areas around the edges of the world as when I made new old worlds to test this bug, only regions around the border corrupted.

This affects new and existing old worlds.

Example video: https://bugs.mojang.com/secure/attachment/141017/Test.mp4