The Bug
When you have a cobweb above the ground and you drop a gravity affected block (i.e. gravel) on it; It doesn't fall all the way through it but pops right before it reaches the ground below the cobweb

Replicate

• Place a Cobweb 1 block above the ground
• Drop a gravity affected block on it so it becomes an entity
• Watch it fall but pop before it gets through the cobweb