Other pickups seem fine, just don't pick anything up from that one enemy! Most of the time its loot falls through the floor anyway, maybe it does all the time and pickups are grabs done in time (which as I speculated could play some part in this but I dunno). The wheelchair enemy who has a 100% droprate of 4 quicksilver bullets for instance is a-OK to loot from. And the two trolls down the lighted carpetway also are good to pick up their vial drops from. Just ambush sword guy... kill and move on.