Gravity Blocks turn into any item.

If any gravity block (for example, anvils) enter the end gateway, you quit the world, relog and enter the end gateway, those blocks are going to turn into any item or block in the game.

In fact, it doesn't madder what kind of item it turns into, from blackstone, to command blocks, to blocks that you can't even get from commands or from the creative inventory.

Steps to reproduce:

1. Head to the end (fastest way is with /setblock ~~~ end_portal)
2. Kill the Ender Dragon (the End Gateway should appear)
3. Destroy the top layer of the Gateway
4. Make a pillar behind the End Gateway block
5. (Optional) Quit the world and relog, It doesn't effect this but I'd be safe and sorry if you do this.
6. Place any gravity block on the side of the pillar towards the End Gateway block
7. Quit the world and relog (again)
8. Go into the End Gateway
9. You should see some random items on the floor now

Observed Result: The gravity blocks turn into any random item/block

Expected Result: Nothing should be there/The gravity blocks should appear at the other side

The bug in action: Go to this video by "ItsMe James": https://www.youtube.com/watch?v=9Log6sWZXCo . He can explain this in more detail than me.

!Disclaimer: Sometimes the item on the floor can crash your game if you pick it up if do try this. Make sure you back up your world or do it in a creative world before trying this.

Why is this private?: This is an exploit that is to op, No one else needs to see this.