I have encountered a bug where you cannot loot items from the corpse of a dead player. You can take some however others seem to simply not allow you to loot them from the corpse. I have emptied my inventory etc however it wouldn't let me loot certain items. When this bug happens with ammo you can press triangle to split the stack and keep doing it until 1 round remains on the dead players corpse however you cannot take the final round. It has happened with a hunting knife, a UMP, various food, drink, and ammo.