I have no idea what it could be, but with punches the DL decreases normally. However, when it comes to shooting, business really doesn't work. See the example in the video.

You need to drive the vehicle first

I'm driving

You have enable Custom Weapon Damage?

it's provably some type of custom damage

yes, but only for OnPlayerGiveDamage on players

Maybe that's the priblem

but this is only for person's damage, isn't?

maybe EnableVehicleFriendlyFire();