Steps to reproduce:

1. Set up a space where you can place scaffolding blocks in a way that it falls
2. Keep placing really fast scaffolding blocks in that space
3. You'll end up with something looking like the attached image "TOO MANY SCAFFOLDING BLOCKS"

That happens because when a block falls, it turns into an entity. That means that there aren't any real blocks in that space, so the player can place more.

When these entities reach the bottom and turn into real blocks again, some entities that were in the same location aren't able to turn into blocks and they turn into dropped items.