Whenever you kill someone, and they ragdoll on geometry (particularly next to a wall, or even in a building floor) they fall through the structure/geometry and become unlootable in certain instances.
This can happen when
- a person is right next to the wall, and dies/ragdolls through the geometry/wall to the other side, or into the inside of the building
- a person is in a building floor, and dies/ragdolls through the floors in the building
- a person is on one of those high hills like the hangar hills, or excavated asphalt, and falls through the it etc.
VERY game-breaking, and making killing anyone near geometry near or is impossible to loot.