When you create a world and type 'tp @e[type=zombie, limit=1, sort=nearest] and summon a zombie, when you log out of the world and come back in, you can't place or break command blocks. I don't know the cause of this issue, so I wasn't able to test it a lot. Please do try to reproduce it on the same world, simular coordinates, opening to LAN to use cheats etc. I tried making a world with cheats enabeled by default, it didn't work there, however I might have done something else different that caused the change of outcome.

Seed: 9075672174707764631 

Video: https://www.youtube.com/watch?v=K5ZNin-e8CA

World download: http://www.mediafire.com/file/d4ok5p5zxh5fizd/nope+u+die+(2).zip/file