Assuming a single cell of terrorists, I can't understand why everyone discounts a failure of all of the devices. Isn't the main bomb maker in custody or hiding now? How hard would it be for the "b" team to mess up the recipe? One mistake and all the bombs are fizzles.
what about the possibility of your 'b' team using leftovers rather than making up a new batch since they didn't have their chemist? that would certainly explain the malfunction. 2 weeks+ would cause great deterioration. most bombers probably wouldn't even know that unless their chemist explained it. also.. possibility of simply trying to get rid of leftovers before the bobbies got to them?