When I move or am moved (via Shulker Levitation, for example) into a space that doesn't have a block, but the block above it has a solid block, my head gets stuck in the solid block and I start suffocating. So if I'm walking across grass blocks and move into a space without a block, but the space above that block has a cobblestone block, then I am able to move into the empty space, my head is in the cobblestone's space, and I start suffocating.