>Fogbank

This is a more interesting example- the theory isn't that we lost the tech, but that the new tech was too good, too pure.

The incidentals of the old, 'dirty' way of manufacturing it (that we just spent billions and billions to destroy and clean up) apparently (speculation, since classified) added some unknown impurities that affected its performance.

And either it needed to be redesigned with the new manufacturing process, or go back to the old process to fit the specs of existing weapons or the weapons would need to be redesigned.

We didn't lose the tech, but other 'advances' in both tech and society (not having workers manually handle dangerous stuff) caused an overall regression, not advancement.

It's the EPA DC chlorine case all over again, of 'progress and safety' actually increasing danger and causing overall regression.