Glitch in New Createt Worlds (Blocks 'clones' itselfs in chunks nearby)

I Updated to 1.9 and created a new Flat World, but there comes this Glitch:

1. Create a new flat World (I choose to play in Creativemode in the Configs and my upper blocklayer was Iron_Blocks)
2. Get into the World
3. Set a Block in front of you
4. You (should) see, that the Block also appears in every Chunk nearby/ inside your Renderdistance.
5. Remove the Block
6. The Block disappears; also in the other Chunks

--> I've also take a screenshot of this Glitch!

Sincerly Brosplay3r