Bombs don't detonate.

[Lucas_From_Hell]

From which altitude are they being released? I know it sounds a bit too dumb and obvious, but sometimes it's an error made even by real life pilots (a great example are the Argentine pilots during the Falklands War and the immense amount of bombs who went straight through the hull of RN ships without exploding), simply because the bombs don't have enough time to arm while in the air.