In my part of Europe this is what i fear when ever i see those machines whacking big poles of concrete into the soil, After all this times one is less afraid of this going to happen. Normally the groud will be radared, searched etc but still the duds can be dangerous. I hope the people are all right. 12 to15 % duds on the total of dropped bombs is a lot. And then the dumps after war....
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.
And then there's the occupants of Flanders between Mesen, Wytschaete (Witches' Hat) and Zillebeke living with the spectre of a Great War stack of explosives buried underground that didn't go off during the Messines Ridge offensive on the morning of 7 June 1917. One previously undiscovered lot of explosives went off in 1955 during a lightning storm, which must have frightened the local livestock.
So, is there any consensus about the size and type of the bomb that exploded? It seems various news sites still have troubles distinguishing 250lbs from 250kg. Quite a big difference in the size of the BANG, though... When I was in Munich for work, I've been through that part of the city many times. It's scary to think how many UXOs there are under our feet in Europe!