Persistance Required:1 tag does this:

My minecraft world works for 10 seconds then this happens:

• Chat text doesn't appear

• Mobs don't move

• Mobs, invulnerable or not, can't get hurt

• Leaving and reopening a world will open the world will open a older version of the world (placing a command blocks and then reopening your world will make the command blocks get removed)

• Command blocks cant get activated

• Redstone can't get activated

• Items can't get dropped