If you create a new superflat world and set a preset for "70,46",it crashes the game, and duplicates the launcher.

All I did was try to do the challenge GameChap and Burtie did back in 1.5 where you create a superflat world with the pressure plates as the top layer and TNT as the bottom layer. I did exactly as they did and set the preset as shown in the title, and the game crashed and duplicated a new launcher.