In the Debug World, if you use some of the redstone triggers(Specifically Levers and Pressure Plates[Stone is the only one I used]) They start copying themselves. Whenever the Lever is flicked, it sends out one or two. If a ladder is near by, it clones it as well. If you fly UP into a pressure plate, it spam clones them and crashes the game. This also happens with buttons.
Environment
In the new Debug World (Ah..The Irony.)
This issue has been reported already. It has been linked to the original bugreport.
Please search before reporting any bugs, as it's likely that one exists already.
Also, the spectator gamemode is recommended in the debug world.