Well, what i described is just only the encounter i had, so this particular situation could be explained differently.
The hitbox of the airdrop is gone, so you can shoot through, but the game itselfs knows there is an airdrop so the damage you deal, is not applied on the person.
Proof for the airdrop theory; it is exactly the place where an airdrop could spawn.
*NOTE: I'm not saying this situation is caused by the airdrop bug. And besides that, for the opposite opionion; in the last patch we were told that the airdrop bug has been fixed.