While trying to work on a project in a superflat world in 1.9.2 a bunch of blocks would duplicate all over the world everytime I placed a block this was and I am unsure why this is happening as before I created the world I was in another superflat and blocks were not doing this. I don't know if it is something on my computer or if it is a bug. I had tried creating several different superflats after this started happening and it all turned out the same duplicating blocks...

Update: I went to 1.9 and the blocks were not duplicating but it was still happening in 1.9.2 when I checked it