When using the /summon command to summon two falling sand entities, when one is one block above the other (using two separated command blocks), one of them breaks when hitting the ground.
When using the /summon command to summon two falling sand entities, when one is one block above the other (using two separated command blocks), one of them breaks when hitting the ground.
The first one to land doesn't turn into a solid block for a bit, so the second one will at some point be inside the first's block. This causes the sand to break into an item.