Updating a large amount of Iron Bars causes the game to hang in-game or during the Saving world screen

I generated a flat world with one layer of iron bar, and the world has a memory leak.
 
(it is necessary to wait approximately 15 minutes in the world generate with a layer of iron bar)
 
So:
Step 1: Generate a flat world without structure in peaceful mode in creative
Step 2: Break then replace an iron bar
Step 3: Wait