Gravity blocks - item creation & world corruption

Repro steps:

1. Send a gravity block into the gateway by dropping it from above or using a falling block duper (see the screenshot, there's a redstone wire on the bottom block)
2. Send as many items as you want
3. Relog / restart the server
4. Teleport into the end gate
5. Pick up the block (in the item form)

You can change any gravity block to any other block in the game, including unobtainable items like the reactor or command blocks in survival
Getting invalid client side blocks crashes the client when you pick it up
Getting invalid server side blocks corrupts the world and causes servers to crash, fixed only by deleting the chunk in the world

Original:

(Edit as necessary)
https://youtu.be/BTMgj4W6PtA
https://www.youtube.com/watch?v=ZtwhPrnGrAg