I was copying stuff from my old test world to my new one using MCEdit and 4 of the many item frames that were there just threw 6000 entities on the ground. I've never seen something like this. I also uploaded a YouTube video, to prove it even more Click here I also tried removing the item frames both ways (MCEdit and in the game) but it still happens
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Did you crash?

No, Minecraft didn't crash, just the 6000 entities.

Invalid, because use of 3rd party tools, but maybe related to MC-45568