This is a very annoying crash bug that happens randomly and needs to be fixed. I experienced this crash yesterday and today. The one that happend today resulted in me losing 58 iron blocks that I mined on my no cheats vanilla world. All that iron took months to accumulate. In the pictures I attached it shows the 3 farms I have in my base (a 3 story sugar cane farm, simple zombie xp farm, and a very simple 5 chicken egg farm) that could have no way caused enough lag to make a world crash. On the previous update these same 3 farms never made my game crash. I don't know the main cause of this crash. But it makes the game unplayable unless you want to risk loosing more resources on your world. I lost my iron when I was crafting the blocks into ingots. Then my game crashed. On the picture shown I now only have 12 iron (or a block and 3 iron). This also happens on my creative world, so this doesn't just happen on survival. This also happens on creative aswell. I experienced it agian on a different world, this time it being a lot laggier, but never crashed on me before. This might be a problem with too many entities in one spot, because I had a more advanced farm on my creative world that cause the game to crash. The farm had a lot of chickens in one spot (around 40), but that same farm never caused that many problems on updates before. After doing a quick /kill @e it still crashed afterwards in less than 2-10 minutes.