I've seen estimates that as much as a third of all HE bombs dropped on Germany were duds. As bombs were a seller's market (never enough of them available) manufacturers got away with mediocre quality. Some years back, not far from where I live, they found an 8000 lbs "Cookie". These things were cylindrical, with three impact fuzes on each base, and they all failed to work. I think we will have to live with TNT gifts for the rest of the century.
Another issue is that the Allies cleverly sunk huge amounts of poison gas ammo in the Baltic not far from Denmark, Germany, and Sweden (maybe even Norway if they did that in the Skagerrak). And those chickens will be coming home to roost in the near future as the steel rusts away. I don't think the nerve gases will have lost much of their potency.